Optical assembly for a wide field of view point action camera with low field curvature

ABSTRACT

An optical assembly for a point action camera with a wide field of view includes multiple lens elements configured to provide a field of view in excess of 150 degrees. One or more lens elements has an aspheric surface. The optical assembly exhibits a low inward field curvature of less than 75 microns.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/215,041, filed on Mar. 16, 2014, now U.S. Pat. No. 9,494,772; whichis one of four contemporaneously-filed applications by the sameApplicant and Inventors that are entitled: OPTICAL ASSEMBLY FOR A WIDEFIELD OF VIEW POINT ACTION CAMERA WITH LOW FIELD CURVATURE, applicationSer. No. 14/215,041, now U.S. Pat. No. 9,494,772; OPTICAL ASSEMBLY FOR AWIDE FIELD OF VIEW POINT ACTION CAMERA WITH LOW ASTIGMATISM, applicationSer. No. 14/215,049, now U.S. Pat. No. 9,316,820; OPTICAL ASSEMBLY FOR AWIDE FIELD OF VIEW POINT ACTION CAMERA WITH LOW TRACK LENGTH TO FOCALLENGTH RATIO, application Ser. No. 14/215,056, now U.S. Pat. No.9,091,843; and OPTICAL ASSEMBLY FOR A WIDE FIELD OF VIEW POINT ACTIONCAMERA WITH A LOW SAG ASPHERIC LENS ELEMENT, application Ser. No.14/215,058, now U.S. Pat. No. 9,316,808; which are each herebyincorporated by reference.

BACKGROUND

Point Action cameras, as they are referred to herein, go by many othernames, including point of view cameras (see, e.g.,pointofviewcameras.com), helmet cameras, action cams or action cameras,point of view shooter cams, video action cameras, and extreme sportscameras among others. Brand names include GoPro. Conventional pointaction cameras typically have significant distortion, particularly atthe outer several degrees of the field of view. In addition, astigmatismerrors in conventional point action cameras can negatively impact theappearance of the video images that it captures. It is desired to have apoint action camera that is capable of capturing a wide field of view,or a field of view that is greater than 90 degrees in either or both ofthe horizontal (x) and/or vertical (y) dimensions (or an arbitrary axisnormal to the depth (z) dimension), and perhaps 135-150 degrees or morein the horizontal (x) dimension and/or perhaps 110-120 degrees or morein the vertical (y) dimension, and that is configured with built-indistortion and astigmatism correction.

Distortion in wide field of view cameras has been reduced with imageprocessing software (see, e.g., U.S. Pat. Nos. 8,493,459 and 8,493,460,and US published patent applications nos. US20110216156 andUS20110216157). It is desired however to alternatively provide a pointaction camera, wherein the distortion that is typically inherent in widefield of view systems such as conventional point action cameras iscompensated by an effective and efficient optical design.

Alex Ning describes a six lens design in U.S. Pat. No. 7,023,628 thathas a ratio of total track length (TTL) to effective focal length (EFL),or TTL/EFL, that has a maximum value of 15 over which Ning states thatthe design would not have been considered compact. The Ning six lensdesign also has a minimum value of 8 under which Ning states that thedesign would not achieve the required fish eye field of view. U.S. Pat.No. 7,929,221 describes multiple optical assemblies that each includethree aspheric surfaces on two lens elements and that each have aTTL/EFL ratio between 15 and 25. In an unrelated technical field, U.S.Pat. No. 7,675,694 nonetheless describes multiple optical assembliesthat each include six aspheric surfaces on three lens elements.

It is recognized by the present inventors that it would be advantageousto have a design with a lower TTL/EFL ratio, which takes into accountthe desire for compactness in physical size as well as the desire tohave point action video with a wide field of view without intolerableamounts of distortion and astigmatism errors. It is desired therefore tohave an optical system for a point action camera that has a low TTL/EFLratio and that also achieves a desired wide field of view withtolerable, minimal, insubstantial, insignificant or drastically reduceddistortion and astigmatism characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an optical assembly for a point actioncamera in accordance with certain embodiments.

FIG. 2 is a plot of aspheric sag versus radial distance from the centerof the asphere for the thirteenth surface from the object, or the objectside surface of the seventh lens, in the example optical assemblyillustrated schematically in FIG. 1.

FIG. 3 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the thirteenth surface from the object, orthe object side surface of the seventh lens, in the example opticalassembly illustrated schematically in FIG. 1.

FIGS. 4A-4E and 5A-5E respectively show plots of tangential and sagittalray aberrations for the wide field of view objective assemblyillustrated in FIG. 1.

FIG. 6 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 1 normal to the optical axis(F1), 15 degrees from normal to the optical axis (F2), 35 degrees fromnormal to the optical axis (F3), 55 degrees from normal to the opticalaxis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 7 shows astigmatic field curves for tangential fan (T) and sagittalfan (S) for the optical assembly illustrated schematically at FIG. 1 aswell as the tangential fan (T′) and sagittal fan (S′) for a similaroptical assembly except that the thirteenth optical surface has noaspheric departure.

FIG. 8 schematically illustrates another optical assembly for a pointaction camera in accordance with certain embodiments.

FIG. 9 is a plot of aspheric sag versus radial distance from the centerof the asphere for the thirteenth surface from the object, or the objectside surface of the seventh lens, in the example optical assemblyillustrated schematically in FIG. 8.

FIG. 10 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the thirteenth surface from the object, orthe object side surface of the seventh lens, in the example opticalassembly illustrated schematically in FIG. 8.

FIGS. 11A-11E and 12A-12E respectively show plots of tangential andsagittal ray aberrations for the wide field of view objective assemblyillustrated in FIG. 8.

FIG. 13 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 8 normal to the optical axis(F1), 15 degrees from normal to the optical axis (F2), 35 degrees fromnormal to the optical axis (F3), 55 degrees from normal to the opticalaxis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 14 shows astigmatic field curves for tangential fan (T) andsagittal fan (S) for the optical assembly illustrated schematically atFIG. 9 as well as the tangential fan (T′) and sagittal fan (S′) for asimilar optical assembly except that the thirteenth optical surface hasno aspheric departure.

FIG. 15 schematically illustrates another optical assembly for a pointaction camera in accordance with certain embodiments.

FIG. 16 is a plot of aspheric sag versus radial distance from the centerof the asphere for the thirteenth surface from the object, or the objectside surface of the seventh lens, in the example optical assemblyillustrated schematically in FIG. 15.

FIG. 17 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the thirteenth surface from the object, orthe object side surface of the seventh lens, in the example opticalassembly illustrated schematically in FIG. 15.

FIGS. 18A-18E and 19A-19E respectively show plots of tangential andsagittal ray aberrations for the wide field of view objective assemblyillustrated in FIG. 15.

FIG. 20 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 15 normal to the opticalaxis (F1), 15 degrees from normal to the optical axis (F2), 35 degreesfrom normal to the optical axis (F3), 55 degrees from normal to theoptical axis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 21 shows astigmatic field curves for tangential fan (T) andsagittal fan (S) for the optical assembly illustrated schematically atFIG. 16 as well as the tangential fan (T′) and sagittal fan (S′) for asimilar optical assembly except that the thirteenth optical surface hasno aspheric departure.

FIG. 22 schematically illustrates another optical assembly for a pointaction camera in accordance with certain embodiments.

FIG. 23 is a plot of aspheric sag versus radial distance from the centerof the asphere for the thirteenth surface from the object, or the objectside surface of the seventh lens, in the example optical assemblyillustrated schematically in FIG. 22.

FIG. 24 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the thirteenth surface from the object, orthe object side surface of the seventh lens, in the example opticalassembly illustrated schematically in FIG. 22.

FIG. 25 is a plot of aspheric sag versus radial distance from the centerof the asphere for the fourteenth surface from the object, or the imageside surface of the seventh lens, in the example optical assemblyillustrated schematically in FIG. 22.

FIG. 26 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the fourteenth surface from the object, orthe image side surface of the seventh lens, in the example opticalassembly illustrated schematically in FIG. 22.

FIGS. 27A-27E and 28A-28E respectively show plots of tangential andsagittal ray aberrations for the wide field of view objective assemblyillustrated in FIG. 22.

FIG. 29 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 22 normal to the opticalaxis (F1), 15 degrees from normal to the optical axis (F2), 35 degreesfrom normal to the optical axis (F3), 55 degrees from normal to theoptical axis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 30 shows astigmatic field curves for tangential fan (T) andsagittal fan (S) for the optical assembly illustrated schematically atFIG. 22 as well as the tangential fan (T′) and sagittal fan (S′) for asimilar optical assembly except that the thirteenth optical surface hasno aspheric departure.

BRIEF DESCRIPTION OF THE TABLES

Table 1 includes an Optical Design Prescription in accordance with afirst example embodiment.

It is here noted that the Glass code=xxxxxx.yyyyyy describes therefractive index (xxxxxx) and dispersion (yyyyyy). For example:516800.641672 means that the refractive index nd=1.517 and thedispersion vd=64.2, each for the “d-line”, where the “d-line”=587.5618 dYellow helium line He. This formula applies also to Tables 4, 7 and 10.

Table 2 includes Aspheric Sag Data Relative to Best Fit Sphere (SAG<20um) in accordance with the first example embodiment.

Table 3 includes quantitative data for a Design of an aspheric elementE7 that enables multiple order astigmatism correction in accordance withthe first example embodiment.

Table 4 includes an Optical Design Prescription in accordance with asecond example embodiment.

Table 5 includes Aspheric Sag Data Relative to Best Fit Sphere (SAG<17um) in accordance with the second example embodiment.

Table 6 includes quantitative data for a Design of an aspheric elementE7 that enables multiple order astigmatism correction in accordance withthe second example embodiment.

Table 7 includes an Optical Design Prescription in accordance with athird example embodiment.

Table 8 includes Aspheric Sag Data Relative to Best Fit Sphere (SAG<17um) in accordance with the third example embodiment. The best fit spherebfs in this example is about 9.3 mm (bfs=9.287 mm)

Table 9 includes quantitative data for a Design of an aspheric elementE7 that enables multiple order astigmatism correction in accordance withthe third example embodiment.

Table 10 includes an Optical Design Prescription in accordance with afourth example embodiment.

Table 11 includes Aspheric Sag data for a first of two aspheric lenssurfaces (A1) of a single aspheric lens element of a wide field of viewoptical assembly for a point action camera in accordance with the fourthexample embodiment. In this example, the Data is Relative to a Best FitSphere of about 9.15 mm (Rbfs=9.153 mm).

Table 12 includes Aspheric Sag data for a second of two aspheric lenssurfaces (A2) of the single aspheric lens element of the fourth exampleembodiment. In this example, the Data is Relative to Best Fit Sphere ofabout −37.5 mm (Rbfs=−37.5 mm). The minus sign is indicative of a conveximage facing surface of the single aspheric lens element of the opticalassembly in accordance with the fourth example embodiment.

Table 13 includes quantitative asphere analysis data for the objectfacing surface A1 of a single aspheric lens element E7(A)(A) thatenables multiple order astigmatism correction in accordance with thefourth example embodiment.

Table 14 includes quantitative asphere analysis data for the imagefacing surface A2 of a single aspheric lens element E7(A)(A) thatenables multiple order astigmatism correction in accordance with thefourth example embodiment.

TABLE 1 RDY THI RMD GLA >OBJ: INFINITY 2500.000000  1: 13.10000 1.750000800999.349787  2: 3.30000 2.219000  3: 40.00000 1.000000 496998.815947 4: 3.10000 1.390000  5: 9.00000 2.450000 846670.237912  6: −11.635000.606000 STO: INFINITY 0.200000  8: 14.35000 1.500000 883003.408069  9:−4.75000 0.359000 10: −4.03500 1.000000 846670.237912 11: 3.950002.745000 618000.633335 12: −5.22500 0.100000 13: 8.33000 1.800000516800.641673 SLB: “A1” ASP: A: −.902607E−03 B: −.512165E−04 C:0.149690E−04 D: −.154499E−05 E: 0.561297E−07 14: −37.50000 0.100000 15:INFINITY 1.000000 516800.641673 16: INFINITY 2.681803 17: INFINITY0.500000 516800.641673 18: INFINITY 0.400000 IMG: INFINITY 0.000000SPECIFICATION DATA FNO 2.70000 DIM MM WL 650.00 586.00 486.00 450.00 WTW1 1 1 1 XAN 0.00000 0.00000 0.00000 0.00000 0.00000 YAN 0.00000 15.0000035.00000 55.00000 75.00000

TABLE 2 ASPHERIC EQUATION

WHERE THE ASPHERIC COEFFICIENTS ARE AS FOLLOWS: A: −.902607E−03 B:−.512165E−04 C: 0.149690E−04 D: −.154499E−05 E: 0.561297E−07 ASPH SAG Y(Z) SPHERE SAG SAG DIFFERENCE 0.000000 0.000000 0.000000 0.0000000.132000 0.001192 0.001046 −0.000146 0.264000 0.004764 0.004184−0.000580 0.396000 0.010711 0.009418 −0.001293 0.528000 0.0190210.016750 −0.002271 0.660000 0.029679 0.026187 −0.003492 0.7920000.042663 0.037736 −0.004927 0.924000 0.057947 0.051405 −0.0065411.056000 0.075499 0.067205 −0.008294 1.188000 0.095284 0.085149−0.010135 1.320000 0.117262 0.105250 −0.012013 1.452000 0.1413930.127524 −0.013869 1.584000 0.167632 0.151988 −0.015644 1.7160000.195939 0.178664 −0.017275 1.848000 0.226272 0.207572 −0.0187001.980000 0.258593 0.238737 −0.019856 2.112000 0.292861 0.272184−0.020677 2.244000 0.329035 0.307942 −0.021094 2.376000 0.3670700.346042 −0.021028 2.508000 0.406911 0.386518 −0.020393 2.6400000.448494 0.429406 −0.019087 2.772000 0.491752 0.474747 −0.0170052.904000 0.536630 0.522582 −0.014048 3.036000 0.583117 0.572957−0.010159 3.168000 0.631312 0.625924 −0.005389 3.300000 0.6815340.681534 0.000000

TABLE 3 Aspheric Aspheric Slope Height (Y) Sag (um) Height (Y) (um/mm)0.000 0.000 0 0 0.132 −0.146 0.132 −1.106060606 0.264 −0.580 0.264−3.287878788 0.396 −1.293 0.396 −5.401515152 0.528 −2.271 0.528−7.409090909 0.660 −3.492 0.66 −9.25 0.792 −4.927 0.792 −10.871212120.924 −6.541 0.924 −12.22727273 1.056 −8.294 1.056 −13.28030303 1.188−10.135 1.188 −13.9469697 1.320 −12.013 1.32 −14.22727273 1.452 −13.8691.452 −14.06060606 1.584 −15.644 1.584 −13.4469697 1.716 −17.275 1.716−12.35606061 1.848 −18.700 1.848 −10.79545455 1.980 −19.856 1.98−8.757575758 2.112 −20.677 2.112 −6.21969697 2.244 −21.094 2.244−3.159090909 2.376 −21.028 2.376 0.5 2.508 −20.393 2.508 4.8106060612.640 −19.087 2.64 9.893939394 2.772 −17.005 2.772 15.77272727 2.904−14.048 2.904 22.40151515 3.036 −10.159 3.036 29.46212121 3.168 −5.3893.168 36.13636364 3.300 0.000 3.3 40.82575758

TABLE 4 RDY THI GLA OBJ: INFINITY 2500.000000    1: 10.25000 1.500000729157.546800    2: 3.15000 1.802000    3: 6.25000 1.000000729157.546800    4: 2.24000 1.029000    5: 11.23500 3.220000808095.227608    6: INFINITY 0.250000 STO: INFINITY 0.257000    8:−102.50000 1.225000 729157.546800    9: −4.20000 0.100000   10: 8.550001.710000 922860.188969   11: 3.72500 2.200000 618000.633335   12:−29.92000 0.806000 >13: 8.00971 1.500000 496999.815459 SLB: “A1” ASP: A:−.170738E−02 B: 0.959932E−04 C: −.862671E−05 D: 0.442436E−06   14:−100.00000 0.250000   15: INFINITY 0.500000 516330.641420   16: INFINITY2.050000   17: INFINITY 0.500000 516330.641420   18: INFINITY 0.400000  19: INFINITY 0.000000 IMG: INFINITY 0.000000 SPECIFICATION DATA FNO2.70000 DIM MM WL 650.00 586.00 486.00 450.00 WTW 1 1 1 1 XAN 0.000000.00000 0.00000 0.00000 0.00000 YAN 0.00000 15.00000 35.00000 55.0000075.00000 VUY 0.00000 0.00000 0.15000 0.25000 0.40000 VLY 0.00000 0.000000.15000 0.25000 0.40000

TABLE 5 ASPHERIC EQUATION

RADIUS OF BEST SPHERE = 9.447 WHERE THE ASPHERIC COEFFICIENTS ARE ASFOLLOWS: A: −0.170738E−02 B:  0.959932E−04 C: −0.862671E−05 D: 0.442436E−06 Y ASPH SAG SPHERE SAG SAG DIFFERENCE 0.000000 0.0000000.000000 0.000000 0.115000 0.000825 0.000700 −0.000125 0.230000 0.0032980.002800 −0.000498 0.345000 0.007409 0.006302 −0.001107 0.4600000.013144 0.011207 −0.001938 0.575000 0.020483 0.017516 −0.0029660.690000 0.029399 0.025233 −0.004165 0.805000 0.039863 0.034362−0.005501 0.920000 0.051843 0.044906 −0.006936 1.035000 0.0653000.056871 −0.008430 1.150000 0.080198 0.070261 −0.009937 1.2650000.096493 0.085082 −0.011411 1.380000 0.114145 0.101343 −0.0128021.495000 0.133109 0.119049 −0.014060 1.610000 0.153340 0.138210−0.015131 1.725000 0.174794 0.158834 −0.015961 1.840000 0.1974250.180931 −0.016494 1.955000 0.221188 0.204512 −0.016676 2.0700000.246038 0.229588 −0.016450 2.185000 0.271933 0.256171 −0.0157622.300000 0.298836 0.284274 −0.014561 2.415000 0.326717 0.313913−0.012805 2.530000 0.355562 0.345100 −0.010461 2.645000 0.3853760.377853 −0.007523 2.760000 0.416200 0.412189 −0.004012 2.8750000.448125 0.448125 0.000000

TABLE 6 Aspheric Aspheric Slope Height (Y) Sag (um) Height (Y) (um/mm)0.000 0.000 0.000 0.000 0.115 −0.125 0.115 −1.087 0.230 −0.498 0.230−3.243 0.345 −1.107 0.345 −5.296 0.460 −1.938 0.460 −7.226 0.575 −2.9660.575 −8.939 0.690 −4.165 0.690 −10.426 0.805 −5.501 0.805 −11.617 0.920−6.936 0.920 −12.478 1.035 −8.430 1.035 −12.991 1.150 −9.937 1.150−13.104 1.265 −11.411 1.265 −12.817 1.380 −12.802 1.380 −12.096 1.495−14.060 1.495 −10.939 1.610 −15.131 1.610 −9.313 1.725 −15.961 1.725−7.217 1.840 −16.494 1.840 −4.635 1.955 −16.676 1.955 −1.583 2.070−16.450 2.070 1.965 2.185 −15.762 2.185 5.983 2.300 −14.561 2.300 10.4432.415 −12.805 2.415 15.270 2.530 −10.461 2.530 20.383 2.645 −7.523 2.64525.548 2.760 −4.012 2.760 30.530 2.875 0.000 2.875 34.887

TABLE 7 RDY THI RMD GLA OBJ: INFINITY INFINITY  1: 9.83500 1.500000729157.546800  2: 3.20000 1.915000  3: 7.46000 1.000000 618000.633335 4: 2.22000 1.028000  5: 13.51456 3.000000 808095.227608  6: −15.504770.211500 >STO: INFINITY 0.285400  8: −48.00000 1.160000 882997.407651 9: −5.00000 0.285400 10: INFINITY 1.000000 808095.227608 11: 3.700002.500000 618000.633335 12: −7.20000 0.250000 13: 8.64801 1.500000487490.702363 SLB: “A1” ASP: A: −.980930E−03 B: 0.996294E−04 C:−.898355E−05 D: 0.464096E−06 14: INFINITY 0.616800 15: INFINITY 0.500000516330.641420 16: INFINITY 2.647000 17: INFINITY 0.500000 516330.64142018: INFINITY 0.400000 IMG: INFINITY 0.000000 SPECIFICATION DATA FNO2.70000 DIM MM WL 650.00 600.00 550.00 500.00 450.00 REF 3     WTW 1 1 11 1 XAN 0.00000 0.00000 0.00000 0.00000 0.00000 YAN 0.00000 15.0000035.00000 55.00000 75.00000 WTF 1.00000 2.00000 1.00000 1.00000 1.00000VUY 0.00000 0.00000 0.15000 0.25000 0.40000 VLY 0.00000 0.00000 0.150000.25000 0.40000

TABLE 8 ASPHERIC EQUATION

ASPHERIC CONSTANTS A: −.980930E−03 B: 0.996294E−04 C: −.898355E−05 D:0.464096E−06 Y ASPH SAG SPHERE SAG SAG DIFFERENCE 0.000000 0.0000000.000000  0.000000 0.115000 0.000764 0.000712 −0.000052 0.2300000.003056 0.002849 −0.000208 0.345000 0.006871 0.006411 −0.0004600.460000 0.012200 0.011400 −0.000800 0.575000 0.019033 0.017818−0.001215 0.690000 0.027358 0.025669 −0.001690 0.805000 0.0371620.034956 −0.002206 0.920000 0.048429 0.045683 −0.002746 1.0350000.061144 0.057855 −0.003289 1.150000 0.075293 0.071479 −0.0038141.265000 0.090862 0.086560 −0.004302 1.380000 0.107840 0.103106−0.004734 1.495000 0.126216 0.121124 −0.005092 1.610000 0.1459820.140624 −0.005357 1.725000 0.167131 0.161615 −0.005516 1.8400000.189660 0.184107 −0.005554 1.955000 0.213570 0.208111 −0.0054592.070000 0.238863 0.233639 −0.005224 2.185000 0.265549 0.260705−0.004844 2.300000 0.293645 0.289322 −0.004323 2.415000 0.3231800.319505 −0.003675 2.530000 0.354201 0.351270 −0.002931 2.6450000.386778 0.384633 −0.002145 2.760000 0.421023 0.419614 −0.0014092.875000 0.457098 0.456230 −0.000867

TABLE 9 Aspheric Aspheric Slope Height (Y) Sag (um) Height (Y) (um/mm)0.000 0.000 0 0 0.115 −0.052 0.115 −0.452173913 0.230 −0.208 0.23−1.356521739 0.345 −0.460 0.345 −2.191304348 0.460 −0.800 0.46−2.956521739 0.575 −1.215 0.575 −3.608695652 0.690 −1.690 0.69−4.130434783 0.805 −2.206 0.805 −4.486956522 0.920 −2.746 0.92−4.695652174 1.035 −3.289 1.035 −4.72173913 1.150 −3.814 1.15−4.565217391 1.265 −4.302 1.265 −4.243478261 1.380 −4.734 1.38−3.756521739 1.495 −5.092 1.495 −3.113043478 1.610 −5.357 1.61−2.304347826 1.725 −5.516 1.725 −1.382608696 1.840 −5.554 1.84−0.330434783 1.955 −5.459 1.955 0.826086957 2.070 −5.224 2.072.043478261 2.185 −4.844 2.185 3.304347826 2.300 −4.323 2.3 4.5304347832.415 −3.675 2.415 5.634782609 2.530 −2.931 2.53 6.469565217 2.645−2.145 2.645 6.834782609 2.760 −1.409 2.76 6.4 2.875 −0.867 2.8754.713043478

TABLE 10 >OBJ: INFINITY INFINITY  1: 9.75000 1.600000 729157.546800  2:3.05000 1.770000  3: 6.30000 1.100000 729157.546800  4: 2.20000 0.968200 5: 16.28500 2.617000 922860.188969  6: −15.33500 0.256000 STO: INFINITY0.294000  8: −16.50000 1.250000 618000.633335  9: −3.95000 0.100000 10:50.00000 1.000000 922860.188969 11: 6.00000 2.300000 618000.633335 12:−7.46500 0.250000 13: 9.64694 1.583000 496999.815459 SLB: “A1” ASP: A:0.171027E−03 B: 0.780901E−04 C: −.170715E−05 D: −.594285E−06 14:−18.95073 0.250000 SLB: “A2” ASP: A: 0.141992E−02 B: −.879215E−05 C:0.135290E−04 D: −.133102E−05 15: INFINITY 0.500000 516330.641420 SLB:“ircut” 16: INFINITY 3.736401 17: INFINITY 0.500000 516330.641420 18:INFINITY 0.400000 IMG: INFINITY 0.000000 SPECIFICATION DATA FNO 2.70000DIM MM WL 650.00 600.00 550.00 500.00 450.00 REF 3     WTW 1 1 1 1 1 XAN0.00000 0.00000 0.00000 0.00000 0.00000 YAN 0.00000 15.00000 35.0000055.00000 75.00000 WTF 1.00000 2.00000 1.00000 1.00000 1.00000

TABLE 11 ASPHERIC EQUATION

ASPHERIC CONSTANTS A:  0.171027E−03 B:  0.780901E−04 C: −0.170715E−05 D:−0.594285E−06 Y ASPH SAG SPHERE SAG SAG DIFFERENCE 0.000000 0.0000000.000000 −0.005251 0.115000 0.000686 0.000722 −0.005214 0.2300000.002743 0.002890 −0.005103 0.345000 0.006174 0.006504 −0.0049200.460000 0.010982 0.011566 −0.004666 0.575000 0.017173 0.018079−0.004345 0.690000 0.024755 0.026045 −0.003960 0.805000 0.0337380.035469 −0.003520 0.920000 0.044138 0.046354 −0.003034 1.0350000.055971 0.058706 −0.002516 1.150000 0.069262 0.072532 −0.0019811.265000 0.084040 0.087838 −0.001453 1.380000 0.100337 0.104630−0.000958 1.495000 0.118196 0.122919 −0.000527 1.610000 0.1376600.142712 −0.000198 1.725000 0.158779 0.164020 −0.000009 1.8400000.181603 0.186854  0.000000 1.955000 0.206181 0.211224 −0.0002072.070000 0.232553 0.237145 −0.000658 2.185000 0.260740 0.264629−0.001362 2.300000 0.290739 0.293691 −0.002299 2.415000 0.3224980.324346 −0.003403 2.530000 0.355903 0.356611 −0.004542 2.6450000.390747 0.390505 −0.005493 2.760000 0.426698 0.426045 −0.0059042.875000 0.463253 0.463253 −0.005251

TABLE 12 ASPHERIC EQUATION

ASPHERIC CONSTANTS A:  0.141992E-02 B: −0.879215E-05 C:  0.135290E-04 D:−0.133102E-05 Y ASPH SAG SPHERE SAG SAG DIFFERENCE 0.000000  0.000000 0.000000 0.000000 0.120000 −0.000380 −0.000192 0.000188 0.240000−0.001515 −0.000768 0.000747 0.360000 −0.003396 −0.001728 0.0016680.480000 −0.006005 −0.003072 0.002932 0.600000 −0.009317 −0.0048000.004517 0.720000 −0.013301 −0.006913 0.006389 0.840000 −0.017919−0.009409 0.008510 0.960000 −0.023123 −0.012290 0.010833 1.080000−0.028860 −0.015555 0.013304 1.200000 −0.035063 −0.019205 0.0158591.320000 −0.041660 −0.023239 0.018421 1.440000 −0.048563 −0.0276580.020905 1.560000 −0.055674 −0.032462 0.023212 1.680000 −0.062880−0.037651 0.025230 1.800000 −0.070056 −0.043225 0.026831 1.920000−0.077066 −0.049184 0.027882 2.040000 −0.083766 −0.055529 0.0282372.160000 −0.090017 −0.062259 0.027758 2.280000 −0.095693 −0.0693760.026317 2.400000 −0.100705 −0.076878 0.023827 2.520000 −0.105031−0.084767 0.020264 2.640000 −0.108758 −0.093043 0.015715 2.760000−0.112139 −0.101705 0.010433 2.880000 −0.115670 −0.110755 0.0049153.000000 −0.120192 −0.120192 0.000000

TABLE 13 Aspheric Aspheric Slope Height (Y) Sag (um) Height (Y) (um/mm)0.000 −5.251 0 0.000 0.115 −5.214 0.115 0.322 0.230 −5.103 0.23 0.9650.345 −4.920 0.345 1.591 0.460 −4.666 0.46 2.209 0.575 −4.345 0.5752.791 0.690 −3.960 0.69 3.348 0.805 −3.520 0.805 3.826 0.920 −3.034 0.924.226 1.035 −2.516 1.035 4.504 1.150 −1.981 1.15 4.652 1.265 −1.4531.265 4.591 1.380 −0.958 1.38 4.304 1.495 −0.527 1.495 3.748 1.610−0.198 1.61 2.861 1.725 −0.009 1.725 1.643 1.840 0.000 1.84 0.078 1.955−0.207 1.955 −1.800 2.070 −0.658 2.07 −3.922 2.185 −1.362 2.185 −6.1222.300 −2.299 2.3 −8.148 2.415 −3.403 2.415 −9.600 2.530 −4.542 2.53−9.904 2.645 −5.493 2.645 −8.270 2.760 −5.904 2.76 −3.574 2.875 −5.2512.875 5.678

TABLE 14 Aspheric Aspheric Slope Height (Y) Sag (um) Height (Y) (um/mm)0.000 0 0 0.000 0.120 0.188 0.12 1.567 0.240 0.747 0.24 4.658 0.3601.668 0.36 7.675 0.480 2.932 0.48 10.533 0.600 4.517 0.6 13.208 0.7206.389 0.72 15.600 0.840 8.51 0.84 17.675 0.960 10.833 0.96 19.358 1.08013.304 1.08 20.592 1.200 15.859 1.2 21.292 1.320 18.421 1.32 21.3501.440 20.905 1.44 20.700 1.560 23.212 1.56 19.225 1.680 25.23 1.6816.817 1.800 26.831 1.8 13.342 1.920 27.882 1.92 8.758 2.040 28.237 2.042.958 2.160 27.758 2.16 −3.992 2.280 26.317 2.28 −12.008 2.400 23.8272.4 −20.750 2.520 20.264 2.52 −29.692 2.640 15.715 2.64 −37.908 2.76010.433 2.76 −44.017 2.880 4.915 2.88 −45.983 3.000 0 3 −40.958

DETAILED DESCRIPTIONS OF THE EMBODIMENTS

An optical assembly for a point action camera having a wide field ofview includes multiple lens elements including an aspheric surface. Theoptical assembly is configured to provide a wide field of view, which isin certain embodiments in excess of 150 degrees. The optical assemblyincludes an inward field curvature of less than approximately 75microns. In certain embodiments, the inward field curvature is less thanapproximately 60 microns. In other embodiments, the inward fieldcurvature is less than approximately 50 microns or less.

Another optical assembly for a point action camera having a wide fieldof view, comprising multiple lens elements, including an asphericsurface, configured to provide a field of view in excess of 150 degreesthat comprises a longitudinal astigmatism of 0.7 mm or less.

Another optical assembly for a point action camera having a wide fieldof view, comprising multiple lens elements, including an asphericsurface, configured to provide a field of view in excess of 150 degreesthat comprises a ratio of total track length to effective focal lengththat is less than 8.

Another optical assembly for a point action camera having a wide fieldof view, comprising multiple lens elements, including an asphericsurface with an approximately 30 microns or less sag and anapproximately 25 microns/millimeter aspheric sag slope, configured toprovide a field of view in excess of 150 degrees.

In certain embodiments, the longitudinal astigmatism comprisesapproximately 0.6 mm or less, or in other embodiments, approximately 0.5mm or less, or approximately 0.3 mm or less, or approximately 0.2 mm orless, or approximately 0.1 mm or less in certain embodiments.

From object end to image end, an optical assembly in accordance withcertain embodiments includes a first optical group and a second opticalgroup, wherein the first optical group is configured to collect light ata wide field of view and a second optical group is configured to correctdistortion or astigmatism error or both. An aperture stop may bedisposed between said first and second optical groups.

The second optical group may be configured to correct astigmatism error.The second optical group may include multiple lens elements including anultimate or penultimate lens element that is configured with an asphericdeparture to correct astigmatism error. In certain embodiments, theultimate lens element of the optical lens assembly includes an asphericdeparture. In certain embodiments, an object facing surface of theultimate lens element has an aspheric departure. The optical assemblymay include seven lens elements.

A second optical group (from object to image) may include four lenselements. The second optical group may include, from object side toimage side, a first singlet, a doublet and a second singlet. The firstsinglet may include a biconvex or plano-convex or quasi-plano-convexlens. The second singlet may include a biconvex, or convexo-plano orconvexo-quasi-plano lens.

The first optical group may include two or more convexo-concave ormeniscus lenses. The first optical group may include a biconvex lens.The doublet may include in certain embodiments, from object side toimage side, a biconcave lens and a biconvex lens.

A third optical group may be disposed between the first and secondoptical groups. The third optical group may include a biconvex lens.

The lateral chromatic aberration (LCA) of an optical assembly inaccordance with certain embodiments may be less than approximately threepixels. The LCA in certain embodiments may be less than approximatelytwo pixels. The LCA in certain embodiments may be less thanapproximately five microns or less than approximately three microns.

An optical assembly in accordance with certain embodiments may include asingle aspheric lens element, which may be the only aspheric lenselement within the optical assembly. In these embodiments, lens elementsother than the single aspheric lens element have spherical or planarlens surfaces, or both, each without significant aspheric departures.

An optical assembly in accordance with certain embodiments may include asingle aspheric lens surface, which may be the only aspheric lenssurface within the optical assembly. In these embodiments, lens surfacesother than the single aspheric lens surface have spherical or planarlens surfaces, or both, each without significant aspheric departures.

Another optical assembly in accordance with certain embodiments includesonly one aspheric lens element. Subsets of these embodiments includelens elements that have two aspheric surfaces, i.e., both the objectfacing surface and the image facing surface of a same aspheric lenselement are configured with aspheric departure. Other subsets of theseembodiments include lens elements that have only a single aspheric lenssurface, i.e., either the object facing surface or the image facingsurface is aspheric, while the other surface does not have significantaspheric departure or to tolerance one of the lens surfaces isspherical.

Another optical assembly in accordance with certain embodiments includesonly one aspheric lens surface. This optical assembly includes a singleaspheric lens surface configured to correct astigmatism.

A digital point action camera is provided that includes any of theoptical assemblies described herein, along with an image sensor disposedapproximately at a focal plane of the optical assembly. A digital camerahousing includes electronics and a user interface, and contains anddurably affixes the optical assembly and the image sensor in opticallyeffective relative disposition. The housing may be waterproof and mayinclude shock absorbing material to withstand shocks such as may becaused by collisions or sudden acceleration or high speed or highfrequency jitter.

An aspheric lens element is provided for an optical assembly of a widefield of view point action camera in accordance with any of theembodiments of optical assemblies or point action cameras describedherein. In certain embodiments, one or both surfaces has anapproximately 30 microns or less sag and an approximately 25microns/millimeter or less aspheric sag slope. In a specific embodiment,only a single lens surface has aspheric departure. In anotherembodiment, both the image facing surface and the object facing surfaceof the same lens element include aspheric departures.

In addition, combinations of features described herein, above and/orbelow, with regard to different embodiments form additional embodimentsof optical assemblies, point action cameras and aspheric lens elements.

Several example embodiments are described below and are illustrated inthe accompanying drawings. In certain embodiments, a seventh lenselement, from object to image, is the only lens element of the opticalassembly that includes one or two surfaces aspheric surfaces. In certainembodiments, the object facing surface of the seventh lens element orthe thirteenth surface of the optical assembly has an asphericdeparture, while the image facing surface of the seventh lens element orthe fourteenth surface of the optical assembly may have an asphericsurface also, or a spherical surface that may be slightly curved orquasi-planar, or may have a significant spherical curvature, or may beapproximately planar. Alternatively, the fourteenth surface may be theonly surface of the optical assembly that has an aspheric departure,while the thirteenth surface has a planar, quasi-planar or convexspherical curvature. The single lens element of the optical assemblythat has aspheric departure may be the fifth or sixth lens elementrather than the seventh, or may be instead the first or the second lenselement. In these alternative embodiments, one or both surfaces of thesingle aspheric lens element may have aspheric departure, and in thoseembodiments wherein only a single lens surface has aspheric departure,the other surface of the aspheric lens element may be planar, or may bequasi-planar or slightly spherically curved, or may be significantlyspherical.

First Example Embodiment

Referring to the example illustrated schematically in FIG. 1, and in theplots shown in FIGS. 2-7, and quantitatively at Tables 1-3, an opticalassembly in accordance with certain embodiments may include a first lensgroup G1 and a second lens group G2. The first lens group G1 is disposednearer to the object or scene that is being imaged than the second lensgroup G2. The second lens group G2 is disposed between the first lensgroup G1 and the image plane. Together, the first and second opticalgroups G1 and G2 cover a wide field of view, i.e., greater than 120degrees, or in certain embodiment greater than 135 degrees and in othersgreater than 150 degrees and even in certain embodiments significantlyclose to 180 degrees. Alternatively, there may be three, or more, lensgroups instead of two, or the entire optical assembly may form a singlelens group.

Generally speaking, the lens group G1 is configured to collect widefield rays, whereas the lens group G2 is configured to correctaberrations, and particularly distortion and astigmatism. However, theconfiguration can include contributions within the second lens group G2to the collection of wide field rays and/or contributions within thefirst lens group G1 to the correction of aberrations such as distortionand astigmatism. For example, one or more lens elements of the group G2may have a reduced diameter or a material or shape characteristictending to facilitate collection of wide angle rays and/or a surface ofa lens element of group G1 may have aspheric departure configured toassist in the correction of aberrations.

In the embodiment illustrated schematically at FIG. 1, the first lensgroup G1 includes three lenses from furthest to closest to the imageplane, namely lens E1, lens E2 and lens E3.

Lens E1 comprises a convex-concave lens, or meniscus, in the exampleembodiment of FIG. 1. This means that the object facing surface of lensE1, which is the first surface of the optical assembly of the exampleembodiment of FIG. 1, has a convex shape tending to converge incidentlight, while the image facing surface of lens E1, which is the secondsurface of the optical assembly of FIG. 1, has a concave shape tendingto diverge incident light. The lens E1 has a nominal overall opticalpower. This lens E1 may have an extended radius outside of an activeradius which assists and facilitates a wide field of view feature of theoptical assembly of FIG. 1. The physical dimensional characteristics ofthe lenses of the optical assemblies of the embodiments described hereingenerally permit configuring the wide field of view optical assemblywithin a lens barrel of a point action camera and/or within a compact orminiature point action camera.

The lens E1 may be fixed, i.e., relative to the image plane and otherfixed elements of the system. Alternatively, the lens E1 may be movableto permit focusing by automatic or manual actuation using, e.g., a voicecoil motor, piezo, or MEMS coupled to the lens E1. In this alternativeembodiment, a feedback based on analysis of image data received at theimage sensor by a processor, an image processor or an image signalprocessor (ISP). Another optical group may include one or more movablelenses, mirrors or other optics. In this context, a zoom feature mayalso be provided optically and/or electronically. Thus, embodiments ofpoint action cameras described herein include fixed focus, autofocus andautofocus zoom point action cameras. In certain embodiments, the lens E1has an index of refraction at the sodium d line (i.e., 587.5618 nm) ataround 1.8, or n(λ_(d))≈1.8. The dispersion may be around 35. In certainembodiments, the lens E1 may be obtained from the CDGM glass company oftype HZLAF66. The lens E1 has little overall optical power, asmentioned, and serves primarily as a collecting lens that facilitatesthe wide field of view of the optical assembly.

Lens E1 has a larger diameter in order to collect rays at outer edges ofa wide field of view and reduces the field angle for the subsequentlenses of the optical assembly. Lens group G1, and particularly lensesE1 and E2, generally serves to reduce the ray angle for the group G2lens elements. Lens group G2 generally serves to correct distortion andastigmatism errors. The overall optical design of the second lens groupgenerally serves to correct distortion, while the aspheric thirteenthsurface of the optical assembly of FIG. 1 generally serves to correctastigmatism.

The lens element E2 of the lens group G1 has a convexo-concave orplano-concave or quasi-plano-concave structure in the example of FIG. 1.In other words the object facing surface of the lens E2, which is thethird surface of the optical assembly of FIG. 1, has a slightly ornominally convex or planar surface shape, while the image facing surfaceof the lens E2, or the fourth surface of the optical assembly of FIG. 1,has a concave shape tending to diverge incident light rays. In certainembodiments, the lens element E2 may be obtained from the CDGM glasscompany of type HFK61. The lens E2 has a negative overall focal lengthand serves as a diverging optical element. In certain embodiments, thelens E2 has an index of refraction at the sodium d line (i.e., 587.5618nm) at around 1.5, or n(λ_(d))≈1.5. The dispersion may be around 82. Incertain embodiments, the lens element E2 may be obtained from the CDGMglass company of type HZF52A.

The lens element E3 comprises a functionally converging optical elementand has a biconvex structure in the illustrative example of FIG. 1. Boththe object facing and image facing surfaces of the lens element E3,which are the fifth and sixth surfaces of the optical assembly that isillustrated schematically in the example embodiment of FIG. 1, areconvex and tend to converge incident light. The lens element E3 has astrongest positive optical power among the elements of group 1. Incertain embodiments, the lens E3 has an index of refraction at thesodium d line (i.e., 587.5618 nm) at around 1.85, or n(λ_(d))≈0.8. Thedispersion may be around 24. In certain embodiments, the lens element E3may be obtained from the CDGM glass company of type HZF52A.

The lens group G1 has an overall negative focal length, e.g., in oneembodiment EFL (G1)≈−28.4 mm, and serves to collect and convergeincoming light from an object, group of objects or a foreground,background or overall scene, including a wide field of view greater than90 degrees in the horizontal and/or vertical dimensions, and typically135-150 degrees or more in the horizontal and/or 110-120 degrees or morein the vertical. The first two lens elements E1 and E2 have a combinedfocal length in one example of around −2.6 mm, while the lens element E3has a focal length of around +6.3 mm. The rays received from the opticalgroup G1 are not greatly further optically reduced by optical group G2,which has a positive focal length, e.g., in one embodiment EFL (G2) 5.8mm. Optical group G2 serves to correct distortion and astigmatism beforeimages are captured by an image sensor of a point action camera forviewing on a display, and/or for recording or storage or for dataanalysis, monitoring, security or surveillance and/or for transmissionand/or image processing.

The lens group G1 may include two lenses or four lenses, or even onelens or five or more lenses. An aperture stop is disposed between thelens element E3 and the lens element E4 in the example of FIG. 1.Alternatively, an aperture stop is disposed between the lens groups G1and G2, whatever number of optical elements each may comprise. Anaperture stop may be located differently and there may be one or moreadditional apertures within the optical assembly.

The optical group G2 in the example of FIG. 1 includes three or fourlens elements, depending on whether one considers a lens doublet tocomprise a single lens element or two lens elements. The lens group G2in the example of FIG. 1 includes lens E4, lens doublet E5/E6 and lensE7.

Lens E4 may have a biconvex, plano-convex or quasi-plano-convex shape.That is, the object facing surface of lens E4, which is the seventhsurface of the optical assembly of FIG. 1, has a slightly or nominallyconvex or planar shape, while the image facing surface of the lens E4,which is the eighth surface of the optical assembly of FIG. 1, has aconvex shape tending to converge incident light. The lens E4 is disposedin the example of FIG. 1 just on the image side of an aperture stop. Thelens E4 has an overall positive focal length and is functionallyconvergent of incident light after that light has been collected by thelens group G1, has passed through the aperture and has become incidentupon the object facing surface of lens E4, or surface 7 of the overalloptical assembly of FIG. 1. In certain embodiments, the lens E4 has anindex of refraction at the sodium d line (i.e., 587.5618 nm) at around1.88, or n(λ_(d))≈0.9. The dispersion may be around 41. In certainembodiments, the lens E4 may be obtained from the CDGM glass company astype HZLAF68B.

The lens E5 has a biconcave shape while the lens E6 has a biconvexshape. The ninth and tenth surfaces of the optical assembly of FIG. 1,or both of the two surfaces of lens E5, have a concave shape tending todiverge incident light rays, while the eleventh and twelfth surfaces ofthe optical assembly of FIG. 1, or both of the two surfaces of the lensE6, have a convex shape. The twelfth surface of the optical assembly maybe strongly convex and tend to relatively strongly converge incidentlight.

The lenses E5 and E6 are coupled together to form a doublet. In certainembodiments, the image facing surface of lens E5 and the object facingsurface of the lens E6 are in direct contact. An adhesive or otherstandard process of coupling constituent lenses of a doublet may beused, which process may depend upon the materials of the constituentlenses E5 and E6. In certain embodiments, the lens E5 has an index ofrefraction at the sodium d line (i.e., 587.5618 nm) at around 1.85, orn(λ_(d))≈1.8. The dispersion of lens E5 may be around 24. In certainembodiments, the lens E6 has n(λ_(d))≈1.6. In certain embodiments, thelens E6 has a dispersion around 63. In certain embodiments, the lens E5may be obtained from the CDGM glass company of type HZF52A, while thelens E6 may be obtained from the OHARA corporation of type SPHM52. Thedoublet overall serves to configure the light rays before becomingincident upon the lens element E7(A).

Referring to FIG. 1, there a significant advantage to having an opticalassembly in accordance with certain embodiments, wherein the E5/E6doublet, which is shown disposed between the fourth singlet and theasphere in FIG. 1, is configured to correct oblique aberrations.Alternatively, the doublet may be disposed between lens E3 and lens E4.

The lens element E7(A) has a biconvex, or convexo-quasi-plano, orconvexo-plano shape. The object facing surface of the lens E7(A), whichis the thirteenth surface of the optical assembly of FIG. 1, has astrongly convex shape which relatively strongly converges incidentlight. The thirteenth surface of the optical assembly of FIG. 1 is alsoaspheric in this example embodiment. The image facing surface of thelens E7(A), which is the fourteenth surface of the optical assembly ofFIG. 1, has a slightly or nominally convex or planar shape.

Between the fourteenth surface of the optical assembly of FIG. 1 and theimage plane are an IR filter and a cover plate. The IR filter serves tocut out infrared light that can otherwise interfere with the function ofa silicon-based image sensor to collect visible image data. The coverplate serves to protect the image sensor from incident dust, water,oxygen or other corrosive or artifact producing elements that may bepresent in the ambient space surrounding the point action camera. Aseparate baffle may be included to reduce the amount of stray light thatmay become otherwise incident upon the image sensor. Each of the seventhlens, the IR filter and the cover glass may comprise NBK7 Schott glass,such that each may have a refractive index around 1.5 and a dispersionaround 64.

The aspheric departure of the thirteenth optical surface of the opticalassembly in the example embodiment of FIG. 1 serves to advantageouslysignificantly reduce astigmatism errors that would be otherwise inherentin a wide field of view system without an aspheric surface in accordancewith embodiments described herein. Moreover, the advantageous design ofthe optical assembly of FIG. 1, and specifically of the second opticalgroup G2, and more specifically of the lens element E7(A), and stillmore specifically of the object facing surface of the lens element E7(A)permits the optical assembly in this embodiment to have a more efficientmanufacturability than conventional designs that contain multipleaspheric surfaces and/or multiple aspheric lens or other opticalelements.

FIG. 1 has H(θ)/f*θ=1.078. In another similar embodiment H(θ)/f*θ=1.174.In other embodiments, H(θ)/f*θ is greater than 1.2, 1.3, 1.4 and even1.5, and in other embodiments H(θ)/f*θ is approximately 1.

Table 1 generally discloses certain specifications of the exampleoptical assembly that is represented schematically in side view inFIG. 1. Table 1 lists RDY, which is the radius of curvature of theoptical surface. Table 1 lists THI which are the thicknesses of the lenselements and airspaces in sequential order. The row 1 thicknessdescribed the thickness of the first lens element in this embodiment.The row 2 thickness describes the thickness of the spacing between thefirst and second lens elements. The spacing may include air, or forexample dry air or nitrogen gas or vacuum or a noble gas, or a liquidsuch as water. The row 3 describes the thickness of the second lenselement. The row 4 describes the air spacing between the second andthird lens elements in this example. The row 5 describes the thicknessof the third lens element. The row6 describes the thickness of thespacing between the third lens element and the aperture stop. The rowSTO describes the thickness of the air spacing between the aperture stopand the fourth lens element. The row 8 describes the thickness of thefourth lens element. The row 9 describes the air spacing between thefourth lens element and the fifth lens element. The row 10 describes thethickness of the fifth lens element. The row 11 describes the thicknessof the sixth lens element. There is no air thickness between the fifthand sixth lens elements described in the Table 1, because the fifth andsixth lens elements form a doublet in this example, wherein the tenthand eleventh surfaces of the optical assembly are substantially incontact with each other. The row 12 describes the thickness of thespacing between the sixth lens and the seventh lens in this example. Therow 13 describes the thickness of the seventh lens. The row 14 describesthe spacing between the seventh lens and the IR cut filter. The row 15describes the thickness of the IR cut filter. The row 16 describes thespacing thickness between the IR cut filter and the cover plate (e.g.,glass or polymer) for the image sensor. The row 18 describes the spacingbetween the cover plate and the image sensor. The row IMG describes theimage sensor plane.

Seven lens elements E1-E7(A) make up the example optical assembly thatis illustrated schematically at FIG. 1, while a point action cameraincludes the IR cut filter, cover glass and an image sensor packagedwithin a housing along with the optical assembly. The first three lenselements E1-E3 form a first optical group G1 (or E1-E2 form G1 and E3alone forms G2), while the final four lens elements E4-E7(A) form asecond optical group G2 (or E4-E7(A) form a third optical group G3).

The radii of curvature are, in the single aspheric surface example,approximately, i.e., within manufacturing tolerances, the sameeverywhere along the optical surface for each of the first throughtwelfth and fourteenth surfaces of the optical assembly of FIG. 1. Thatis, the coefficients A thru E are each approximately zero for 13 out of14 surfaces of the embodiment of FIG. 1 in the single aspheric surfaceexample of a wide field of view optical assembly for a point actioncamera or compact camera, or miniature camera module or other camera orcamera module including a single aspheric lens element, or only oneaspheric lens element, and exhibiting advantageously low distortion andlow astigmatism. The departures from spherical of the thirteenth surfaceare represented in Table 1 as nonzero coefficients A-E, which correspondmathematically to the coefficients indicated in the formula that isprovided above the Table 2 in the illustration.

This formula with the non-zero coefficients A-E as indicated in Table 1represent the aspheric curvature of the surface 13 of the exampleoptical assembly that is illustrated schematically in FIG. 1.

The specification data of Table 1 represent the first order softwareinputs to complete the optical model. FNO is F number and isapproximately 2.7 in this example. DIM is the dimension which is mm. WLare the wavelengths which are in nanometers, and are 650 nm (red), 586nm (yellow), 486 nm (blue) and 450 nm (violet) in this example. WTF isthe spectral wavelength weighting. XAN and YAN are the x and y fieldangles. VUY and VLY are the vignetting factors for each field. WIDindicates that the example of FIG. 1 is for a wide field of view orWFOV.

Table 2 shows aspherical and spherical SAG data for the thirteenthsurface of the optical assembly of FIG. 1. These data may fit to aformula for SAG for a spherical conic section, e.g.,z(r)=r²/[R+(R²−r²)^(1/2)], wherein for a best sphere of radius 8.330, asin an example embodiment, and a curvature of best sphere, R,corresponding to 0.120047, the different actual radii of curvature, r,for a surface with aspheric departure produce SAG differences comparedto values for a true spherical conic section. These aspherical SAGs foran example thirteenth surface are compared with would be true sphericalSAGs in Table 2 for different distances Y from the vertex center at Y=0to Y=3.3 (mm) in steps of 0.132 (mm).

The aspheric sags in Table 3 that are plotted in FIG. 2 are the asphericsag difference numbers shown in Table 2, which are the differences fromthe best fit sphere sags of the aspheric surface 13. Table 3 also showsvalues of aspheric slope that are plotted in FIG. 3.

FIG. 2 is a plot of aspheric sag versus radial distance, or the dataprovided in the second column from the left in Table 3, for the 13^(th)optical surface from the object in the example optical assemblyillustrated schematically in FIG. 1. The aspheric sag for the 13^(th)surface in this example has a sag minimum between approximately −20 μmand −25 μm between 2 mm and 2.5 mm from the center of the 13^(th) lenssurface. The sag is approximately zero at the center and at the edgeabout 3 mm from the center. The sag plot has a width of approximately1.5 mm at −13 μm. The sag has points of inflection between approximately1 mm and 1.5 mm and 3 mm from the center of the 13^(th) lens surface.

FIG. 3 is a plot of slope of aspheric sag versus radial distance, or thedata provided in the fourth column from the left (or rightmost column)in Table 3, for the 13^(th) optical surface in the example opticalassembly illustrated schematically in FIG. 1. The aspheric slope has aminimum between −10 μm/mm and −20 μm/mm between 1 mm and 1.5 mm from thecenter of the 13^(th) lens surface. The aspheric slope has a largestvalue at the outer edge of the 13^(th) lens surface of around 40 μm/mm.The aspheric slope has points of inflection between around 0.5 mm and 1mm and between 2.5 mm and 3 mm from the center of the 13^(th) lenssurface.

While the asphere may be disposed on other optical surfaces and/or onother lens elements in other embodiments, the 13th surface is selectedin the embodiment illustrated by example in FIG. 1 at least in part dueto the advantageous ratio of the chief ray and marginal ray heights atthat location within the optical assembly. In certain embodiments, oneor more of the 1^(st), 2^(nd), 3^(rd), 4^(th), 12^(th) 13^(th) and/or14^(th) optical surface is/are selected to have aspheric departure overthe 5^(th)-11^(th) surfaces in part due to the ratio of real chief andmarginal ray heights, e.g., of about 2.8 or more, and because ratiosnearer to one tend to provide reduced or even nominal aberrationalcorrection, e.g., of astigmatism, when aspheric departure is accordinglyprovided in corresponding locations within the optical assemblies ofsuch embodiments.

An image sensor, e.g., a charge coupled device (CCD) or a complementarymetal oxide semiconductor (CMOS) device is disposed at the image planein embodiments that include an assembled compact, miniature, pointaction or point of view camera. The optical assembly may be configuredfor later assembly with an image sensor. In this sense, the first andsecond optical groups may be manufactured or assembled separately andlater combined, and in general, parts of the optical assembly or pointaction camera may be separately manufactured or assembled and it ispossible in certain embodiments to replace, restore or realign opticalgroup G1, optical group G2 and/or certain other groups of one or more ofthe lenses or other optical components of the optical assembly or pointaction camera.

FIGS. 4A-4E respectively show plots of tangential ray aberrationsrespectively at 75°, 55°, 35°, 15° and 0° for the wide field of viewobjective assembly illustrated in FIG. 1. FIGS. 4A-4E and 5A-5E showfive pairs of graphs, where each pair illustrates the tangential andsagittal rays at one of these five field angles. The independentvariable (horizontal axis) is the relative coordinate of a ray over thepupil diameter. The vertical axis has a maximum distance measure of+/−approximately three microns or a spread of six microns or less over a150 degree field (which is clearly advantageous over a conventionalsystem that may have, e.g., a 20 micron spread. The vertical axistherefore represents the transverse ray aberration (ray interceptiondistance from the ideal focal point) of a ray passing through a specificrelative pupil position. Graphs 4A-4E (tangential plane) and 5A-5E(sagittal plane) show the transverse ray aberrations for an on-axis raybundle as the bundle is refracted through the lens elements of theoptical assembly of FIG. 1.

In FIGS. 4E and 5E, the performance of the embodiment of FIG. 1 isillustrated for a ray bundle at zero degrees with the optical axis.Graphs 4D and 5D show the performance of the optical assembly of FIG. 1for a ray bundle when the light source is moved providing an incidentangle of 15 degrees with the optical axis. Graphs 4C and 5C show theperformance of the optical assembly of FIG. 1 for a ray bundle when thelight source is moved providing an incident angle of 35 degrees with theoptical axis. Graphs 4B and 5B show the performance of the opticalassembly of FIG. 1 for a ray bundle when the light source is movedproviding an incident angle of 55 degrees with the optical axis. Graphs4A and 5A show the performance of the optical assembly of FIG. 1 for aray bundle when the light source is moved providing an incident angle of75 degrees with the optical axis.

LCA is demonstrated in FIGS. 4A-4E as the separation of the three rayswhich correspond to four different colors or wavelengths, which are inthis example 650 nm, 550 nm, 486 nm and 450 nm.

FIG. 6 illustrates the polychromatic diffraction modulation transferfunction (MTF) plots of contrast vs. spatial frequency for pixels lyingnormal to the optical axis (F1), 15 degrees from normal to the opticalaxis (F2), 35 degrees from normal to the optical axis (F3), 55 degreesfrom normal to the optical axis (F4), and 75 degrees from normal to theoptical axis (F5). Those pixels lying at 75 degrees from normal to theoptical axis would be those at the edge of a point action cameraassembly having a field of view of 150 degrees. A point action camera isprovided herein having a wide field of view of 150 degrees or more.Advantageously high areas under these curves are noticeable in FIG. 6.In accordance with FIGS. 4A-4E, the plots of FIG. 6 demonstrate that theimage quality of the embodiment of FIG. 1 is advantageous.

FIG. 7 shows astigmatic field curves for tangential (e.g., vertical) fan(T) and sagittal (e.g., horizontal) fan (S) for the optical assemblyillustrated schematically at FIG. 1 as well as the tangential fan (T′)and sagittal fan (S′) for a similar optical assembly except that thethirteenth optical surface has no aspheric departure. FIG. 7 shows thatwithout the asphere, the longitudinal astigmatism (T′−S′)˜0.75 mm inthis example. With an aspheric departure in accordance with certainembodiments, e.g., on the thirteenth surface, such as has been describedand illustrated in the example of FIG. 1, the longitudinal astigmatismreduces to approximately zero. Moreover, the field curvature isapproximately flat, e.g., <50 microns, across the sensor format.

An optical design in accordance with the first embodiment exhibits anadvantageous ratio of total track length to effective focal length, orTTL/EFL<8. The specific example illustrated schematically in FIG. 1 hasa calculated TTL to EFL ratio of 7.79 in air, i.e., in physicalgeometrical units for the track and focal lengths, i.e., where the unityindex of refraction or is used throughout in the calculation. Thisexample ratio can also be calculated optically by taking into accountthe indices of refraction of the glasses, polymers and/or other solid,liquid and/or gaseous materials of the cover plate element. When theTTL/EFL ratio is calculated optically as an optical track length over anoptical focal length that takes into account the index of refraction ofthe material that forms the cover glass element (otherwise sometimesdeemed part of a separate image sensor component to be coupled to theoptical assembly), then the ratio is calculated to be approximately7.98, which is based on an optical track length of 21.8 mm and anoptical focal length of 2.73 mm.

The optical assembly of the first example embodiments illustratedschematically in side view at FIG. 1 exhibits a ratio of TTL/EFL that isless than 8. The embodiment of FIG. 1 has a ratio of TTL/EFL that isless than 7.8 in air, and may be approximately 7.79 in air. The specificTTL/EFL ratio of 7.8 for the specific non-limiting example embodimentillustrated at FIG. 1 is based on total track lengths typically between18 and 26 and on effective focal lengths typically between 2.5 and 3.0.In certain embodiments, a ratio of TTL to EFL of 7.79 is achieved with atotal track length of 21.8 mm and an effective focal length of 2.7 mm.An effective focal length of the first group G1 that includes the firstthree lens elements E1, E2 and E3 may be between approximately −20 and−40, or between −24 and −34, or between −26 and −32, or approximately−28, or approximately −29 or −28.4. Among the lens elements of the firstgroup G1, the first two lens elements E1 and E2 may have a combinedfocal length between −1 and −4, or between −1.5 and −3.5, or between −2and −3, or around −2.6 or −2.7 or −2.65 mm, while the third element E3may have a focal length between approximately +4 and +9, or between +5and +8, or between +6 and +7, or around +6.5 or +6.3 or +6.34. The lensGroup G2 including the lenses E4-E7(A) may have an effective focallength between +2 and +10, or between +3 and +9, or between +4 and +8,or between +5 and +7 or around +6 or around +5.8 or +5.84.

In this context, referring again to Table 1, which generally disclosescertain specifications of the example optical assembly that isrepresented schematically in side view in FIG. 1, Table 1 lists radiusof curvature (RDY) values for each of the fourteen optical surfaces,i.e., numbered 1-14 in the left hand column of Table 1, of the sevenlens elements E1-E7(A) that make up the first and second optical groupsG1, G2. Table 1 also lists thickness values (THI) for each of the lenselements and spacings between the lens elements, or of the distancesbetween each adjacent optical surface in the optical assemblyillustrated schematically in side view in FIG. 1. The optical assemblyof FIG. 1 has a TTL/EFL ratio of about 7.79 in air, for a track lengthof approximately 21.8 mm and an effective focal length of approximately2.7 mm. The effective focal length of the lens group G1 is −28.37 mm andthat of the lens group G2 in this example is about 5.84 mm. The lensgroup G1 could be broken down into the first two lenses E1 and E2 whichtogether have an effective (negative) focal length of about −2.65 mm,while the third lens E3 has an effective (positive) focal length ofabout 6.3 mm.

Second Example Embodiment

FIGS. 8-14 and Tables 4-6 illustrate schematically and quantitatively asecond example embodiment. In some respects, the second embodiment isthe same as the first embodiment or similar enough that the descriptionabove is incorporated here and not repeated. As with the firstembodiment, the optical assembly illustrated schematically at FIG. 8includes six or seven lens elements, wherein a first lens group G1 and asecond lens group G2 are separated by an aperture stop disposed betweenthe third and fourth lens elements E3 and E4, respectively. Anotheraperture may be disposed between the second and third lens elements E2and E3, respectively, in certain embodiments. The optical assembly ofFIG. 8 is configured to cover a wide field of view, i.e., greater than120 degrees, or in certain embodiments greater than 135 degrees and inothers greater than 150 degrees and even in certain embodiments 180degrees, or even greater than 180 degrees depending on the degree ofconvex curvature of the first lens surface.

Generally speaking, the lens group G1 is configured to collect widefield rays, whereas the lens group G2 is configured to correctaberrations, and particularly distortion and astigmatism. However, theconfiguration can include contributions within the second lens group G2to the collection of wide field rays and/or contributions within thefirst lens group G1 to the correction of aberrations such as distortionand astigmatism. For example, one or more lens elements of the group G2may have a reduced diameter or a material or shape characteristictending to facilitate collection of wide angle rays and/or a surface ofa lens element of group G1 may have aspheric departure configured toassist in the correction of aberrations such as distortion andastigmatism, and even higher order coma in certain embodiments. Incertain embodiments, the combination of the lens groups G1 and G2 serveto provide wide field of view imaging with advantageously lowdistortion, while a single aspheric lens element serves to provideadvantageously low astigmatism error characteristics for the opticalassembly.

Lens E1 comprises a convex-concave lens, or meniscus, in the exampleembodiment of FIG. 8. This means that the object facing surface of lensE1, which is the first surface of the optical assembly of the exampleembodiment of FIG. 8, has a convex shape tending to converge incidentlight, while the image facing surface of lens E1, which is the secondsurface of the optical assembly of FIG. 8, has a concave shape tendingto diverge incident light. The lens E1 has a nominal overall opticalpower. This lens E1 may have an extended radius outside of an activeradius which assists and facilitates a wide field of view feature of theoptical assembly of FIG. 8. The physical dimensional characteristics ofthe lenses of the optical assemblies of the embodiments described hereingenerally permit configuring the wide field of view optical assemblywithin a lens barrel of a point action camera and/or within a compact orminiature point action camera.

The lens E1 may be fixed, i.e., relative to the image plane and otherfixed elements of the system. Alternatively, the lens E1 may be movableto permit focusing by automatic or manual actuation using, e.g., a voicecoil motor, piezo, or MEMS coupled to the lens E1. In this alternativeembodiment, a feedback based on analysis of image data received at theimage sensor by a processor, an image processor or an image signalprocessor (ISP). Another optical group may include one or more movablelenses, mirrors or other optics. In this context, a zoom feature mayalso be provided optically and/or electronically. Thus, embodiments ofpoint action cameras described herein include fixed focus, autofocus andautofocus zoom point action cameras. In certain embodiments, the lens E1has an index of refraction at the sodium d line (i.e., 587.5618 nm) ataround 1.8, or n(λd)≈1.7 or 1.73. The dispersion may be around 55. Thelens E1 has little overall optical power, as mentioned, and servesprimarily as a collecting lens that facilitates the wide field of viewof the optical assembly.

Lens E1 has a larger diameter in order to collect rays at outer edges ofa wide field of view and reduces the field angle for the subsequentlenses of the optical assembly. Lens group G1, and particularly lens E1and E2, generally serves to reduce the ray angle for the group G2 lenselements. Lens group G2 generally serves to correct distortion andastigmatism errors. The overall optical design of the second lens groupgenerally serves to correct distortion, while the aspheric thirteenthsurface of the optical assembly of FIG. 8 generally serves to correctastigmatism.

The lens element E2 of the lens group G1 has a convexo-concave orplano-concave or quasi-plano-concave structure in the example of FIG. 8.In other words the object facing surface of the lens E2, which is thethird surface of the optical assembly of FIG. 8, has a slightly ornominally convex or planar surface shape, while the image facing surfaceof the lens E2, or the fourth surface of the optical assembly of FIG. 8,has a concave shape tending to diverge incident light rays. The lens E2has a negative overall focal length and serves as a diverging opticalelement. In certain embodiments, the lens E2 has an index of refractionat the sodium d line (i.e., 587.5618 nm) at around 1.7, or n(λd)≈0.73.The dispersion may be around 55 The lens element E3 comprises afunctionally converging optical element and has a convexo-planar, orconvexo-quasi-planar, or alternatively biconvex structure in theillustrative example of FIG. 8. The object facing surface of the lenselement E3, which is the fifth surface of the optical assembly that isillustrated schematically in the example embodiment of FIG. 8, is convexand tends to converge incident light. The image facing surface of thelens element E3, which is the sixth surface of the optical assembly ofFIG. 8, is planar or quasi-planar or only slightly curved convex orconcave. The lens element E3 has a strongest positive optical poweramong the elements of the first optical group G1. In certainembodiments, the lens E3 has an index of refraction at the sodium d line(i.e., 587.5618 nm) at around 1.81, or n(λd)≈1.8. The dispersion may bearound 23. In certain embodiments, the lens element E3 may be obtainedfrom the CDGM glass company of type HZF52A.

The lens group G1 serves to collect and converge incoming light from anobject, group of objects or a foreground, background or overall scene,including a wide field of view greater than 90 degrees in the horizontaland/or vertical dimensions, and typically 135-150 degrees or more in thehorizontal and/or 110-120 degrees or more in the vertical. The raysreceived from the optical group G1 are not greatly further opticallyreduced by optical group G2, which serves to correct distortion andastigmatism before images are captured by an image sensor of a pointaction camera for viewing on a display, and/or for recording or storageor for data analysis, monitoring, security or surveillance and/or fortransmission and/or image processing.

The lens group G1 may include two lenses or four lenses, or even onelens or five or more lenses. An aperture stop is disposed between thelens element E3 and the lens element E4 in the example of FIG. 8.Alternatively, an aperture stop is disposed between the lens groups G1and G2, whatever number of optical elements each may comprise. Anaperture stop may be located differently and there may be one or moreadditional apertures within the optical assembly.

The optical group G2 in the example of FIG. 8 includes three or fourlens elements, depending on whether one considers a lens doublet tocomprise a single lens element or two lens elements. The lens group G2in the example of FIG. 8 includes lens E4, lens doublet E5/E6 and lensE7.

Lens E4 may have a biconvex, plano-convex or quasi-plano-convex shape.That is, the object facing surface of lens E4, which is the seventhsurface of the optical assembly of FIG. 8, has a slightly or nominallyconvex or planar shape, while the image facing surface of the lens E4,which is the eighth surface of the optical assembly of FIG. 8, has aconvex shape tending to converge incident light. The lens E4 is disposedin the example of FIG. 8 just on the image side of an aperture stop. Thelens E4 has an overall positive focal length and is functionallyconvergent of incident light after that light has been collected by thelens group G1, has passed through the aperture and has become incidentupon the object facing surface of lens E4, or surface 7 of the overalloptical assembly of FIG. 8. In certain embodiments, the lens E4 has anindex of refraction at the sodium d line (i.e., 587.5618 nm) at around1.7, or n(λd)≈1.73. The dispersion may be around 55. The lens E5 has abiconcave shape while the lens E6 has a biconvex shape. The ninth andtenth surfaces of the optical assembly of FIG. 8, or both of the twosurfaces of lens E5, have a concave shape tending to diverge incidentlight rays, while the eleventh and twelfth surfaces of the opticalassembly of FIG. 8, or both of the two surfaces of the lens E6, have aconvex shape. The twelfth surface of the optical assembly may bestrongly convex and tend to relatively strongly converge incident light.

The lenses E5 and E6 are coupled together to form a doublet. In certainembodiments, the image facing surface of lens E5 and the object facingsurface of the lens E6 are in direct contact. An adhesive or otherstandard process of coupling constituent lenses of a doublet may beused, which process may depend upon the materials of the constituentlenses E5 and E6. In certain embodiments, the lens E5 has an index ofrefraction at the sodium d line (i.e., 587.5618 nm) at around 1.9, orn(λd)≈1.93. The dispersion of lens E5 may be around 19. In certainembodiments, the lens E6 has n(λd)≈1.6. In certain embodiments, the lensE6 has a dispersion around 63. In certain embodiments, the lens E5 maybe obtained from the CDGM glass company of type HZF52A, while the lensE6 may be obtained from the OHARA corporation of type SPHM52. Thedoublet overall serves to configure the light rays before becomingincident upon the lens element E7(A).

Referring to FIG. 8, there a significant advantage to having an opticalassembly in accordance with certain embodiments, wherein the E5/E6doublet, which is shown disposed between the fourth singlet and theasphere in FIG. 8, is configured to correct oblique aberrations.Alternatively, the doublet may be disposed between lens E3 and lens E4.

The lens element E7(A) has a biconvex, or convexo-quasi-plano, orconvexo-plano shape. The object facing surface of the lens E7(A), whichis the thirteenth surface of the optical assembly of FIG. 8, has astrongly convex shape which relatively strongly converges incidentlight. The thirteenth surface of the optical assembly of FIG. 8 is alsoaspheric in this example embodiment. The image facing surface of thelens E7(A), which is the fourteenth surface of the optical assembly ofFIG. 8, has a slightly or nominally convex or planar shape.

Between the fourteenth surface of the optical assembly of FIG. 8 and theimage plane are an IR filter and a cover plate. The IR filter serves tocut out infrared light that can otherwise interfere with the function ofa silicon-based image sensor to collect visible image data. The coverplate serves to protect the image sensor from incident dust, water,oxygen or other corrosive or artifact producing elements that may bepresent in the ambient space surrounding the point action camera. Aseparate baffle may be included to reduce the amount of stray light thatmay become otherwise incident upon the image sensor. Each of the seventhlens, the IR filter and the cover glass may comprise NBK7 Schott glass.

The aspheric departure of the thirteenth optical surface of the opticalassembly in the example embodiment of FIG. 8 serves to advantageouslysignificantly reduce astigmatism errors that would be otherwise inherentin a wide field of view system without an aspheric surface in accordancewith embodiments described herein. Moreover, the advantageous design ofthe optical assembly of FIG. 8, and specifically of the second opticalgroup G2, and more specifically of the lens element E7(A), and stillmore specifically of the object facing surface of the lens element E7(A)permits the optical assembly in this embodiment to have a more efficientmanufacturability than conventional designs that contain multipleaspheric surfaces and/or multiple aspheric lens or other opticalelements.

The optical assembly illustrated schematically at FIG. 8 hasH(θ)/f*θ=1.078. In another similar embodiment H(θ)/f*θ=1.174. In otherembodiments, H(θ)/f*θ is greater than 1.2, 1.3, 1.4 and even 1.5, and inother embodiments H(θ)/f*θ is approximately 1.

Table 4 generally discloses certain specifications of the exampleoptical assembly that is represented schematically in side view in FIG.8. Table 4 lists RDY, which is the radius of curvature of the opticalsurface. Table 4 lists THI which are the thicknesses of the lenselements and airspaces in sequential order. The row 1 thicknessdescribed the thickness of the first lens element in this embodiment.The row 2 thickness describes the thickness of the spacing between thefirst and second lens elements. The spacing may include air, or forexample dry air or nitrogen gas or vacuum or a noble gas, or a liquidsuch as water. The row 3 describes the thickness of the second lenselement. The row 4 describes the air spacing between the second andthird lens elements in this example. The row 5 describes the thicknessof the third lens element. The row6 describes the thickness of thespacing between the third lens element and the aperture stop. The rowSTO describes the thickness of the air spacing between the aperture stopand the fourth lens element. The row 8 describes the thickness of thefourth lens element. The row 9 describes the air spacing between thefourth lens element and the fifth lens element. The row 10 describes thethickness of the fifth lens element. The row 11 describes the thicknessof the sixth lens element. There is no air thickness between the fifthand sixth lens elements described in the Table 1, because the fifth andsixth lens elements form a doublet in this example, wherein the tenthand eleventh surfaces of the optical assembly are substantially incontact with each other. The row 12 describes the thickness of thespacing between the sixth lens and the seventh lens in this example. Therow 13 describes the thickness of the seventh lens. The row 14 describesthe spacing between the seventh lens and the IR cut filter. The row 15describes the thickness of the IR cut filter. The row 16 describes thespacing thickness between the IR cut filter and the cover plate (e.g.,glass or polymer) for the image sensor. The row 18 describes the spacingbetween the cover plate and the image sensor. The row IMG describes theimage sensor plane.

Seven lens elements E1-E7(A) make up the optical assembly, while a pointaction camera includes the IR cut filter, cover glass and image sensoralong with the optical assembly. The first two or three lens elementsform a first optical group G1, while with either the third lens elementforms a second group G2 and the final four lens elements form a thirdoptical group G3 or the final four lens elements form the second opticalgroup G2, respectively.

The radii of curvature are, in the single aspheric surface example,approximately, i.e., within manufacturing tolerances, the sameeverywhere along the optical surface for each of the first thru twelfthand fourteenth surfaces of the optical assembly of FIG. 8. That is, thecoefficients A thru E are each approximately zero for 13 out of 14surfaces of the embodiment of FIG. 8 in the single aspheric surfaceexample. The departures from spherical of the thirteenth surface arerepresented in Table 4 as nonzero coefficients A-E, which correspondmathematically to the coefficients indicated in the formula providedbetween Table 1 and Table 2.

This formula with the non-zero coefficients A-E as indicated in Table 4represents the aspheric curvature of the surface 13 of the exampleoptical assembly that is illustrated schematically in FIG. 8.

The specification data of Table 4 represent the first order softwareinputs to complete the optical model. FNO is F number and isapproximately 2.7 in this example. DIM is the dimension which is mm. WLare the wavelengths which are in nanometers, and are 650 nm (red), 586nm (yellow), 486 nm (blue) and 450 nm (violet) in this example. WTF isthe spectral wavelength weighting. XAN and YAN are the x and y fieldangles. VUY and VLY are the vignetting factors for each field. WIDindicates that the example of FIG. 8 is for a wide field of view orWFOV.

Table 5 shows aspherical and spherical SAG data for the thirteenthsurface of the optical assembly of FIG. 8. These data fit to the formulafor SAG for a spherical conic section that is provided between Table 1and Table 2, or that may be generally or alternatively written as:z(r)=^(r2)/[R+(^(R2)−^(r2))^(1/2)]; wherein for a best sphere of radius8.330, as in an example embodiment, and a curvature of best sphere, R,corresponding to 0.120047, the different actual radii of curvature, r,for a surface with aspheric departure produce SAG differences comparedto values for a true spherical conic section. These aspherical SAGs foran example thirteenth surface are compared with would be true sphericalSAGs in Table 4 for different distances Y from the vertex center at Y=0to Y=3.3 (mm) in steps of 0.132 (mm).

The aspheric sags in Table 6 that are plotted in FIG. 9 are the asphericsag difference numbers shown in Table 5, which are the difference fromthe best fit sphere sags of the aspheric surface 13. Table 6 also showsvalues of aspheric slope that are plotted in FIG. 10.

While the asphere may be disposed on other optical surfaces and/or onother lens elements in other embodiments, the 13th surface is selectedin the embodiment illustrated by example in FIG. 8 at least in part dueto the advantageous ratio of the chief ray and marginal ray heights atthat location within the optical assembly. In certain embodiments, oneor more of the 1st, 2nd, 3rd, 4th, 12th 13th and/or 14th optical surfaceis/are selected to have aspheric departure over the 5th-11th surfaces inpart due to the ratio of real chief and marginal ray heights, e.g., ofabout 2.8 or more, and because ratios nearer to one tend to providereduced or even nominal aberrational correction, e.g., of astigmatism,when aspheric departure is accordingly provided in correspondinglocations within the optical assemblies of such embodiments.

An image sensor, e.g., a charge coupled device (CCD) or a complementarymetal oxide semiconductor (CMOS) device is disposed at the image planein embodiments that include an assembled compact, miniature, pointaction or point of view camera. The optical assembly may be configuredfor later assembly with an image sensor. In this sense, the first andsecond optical groups may be manufactured or assembled separately andlater combined, and in general, parts of the optical assembly or pointaction camera may be separately manufactured or assembled and it ispossible in certain embodiments to replace, restore or realign opticalgroup G1, optical group G2 and/or certain other groups of one or more ofthe lenses or other optical components of the optical assembly or pointaction camera.

FIGS. 11A-11E respectively show plots of tangential ray aberrationsrespectively at 75°, 55°, 35°, 15° and 0° for the wide field of viewobjective assembly illustrated in FIG. 8. FIGS. 11A-11E and 12A-12E showfive pairs of graphs, where each pair illustrates the tangential andsagittal rays at one of these five field angles. The independentvariable (horizontal axis) is the relative coordinate of a ray over thepupil diameter. The vertical axis has a maximum distance measure of+/−approximately three microns or a spread of six microns or less over a150 degree field (which is clearly advantageous over a conventionalsystem that may have, e.g., a 20 micron spread. The vertical axistherefore represents the transverse ray aberration (ray interceptiondistance from the ideal focal point) of a ray passing through a specificrelative pupil position. Graphs 11A-11E (tangential plane) and 12A-12E(sagittal plane) show the transverse ray aberrations for an on-axis raybundle as the bundle is refracted through the lens elements of theoptical assembly of FIG. 8.

In FIGS. 11E and 12E, the performance of the embodiment of FIG. 8 isillustrated for a ray bundle at zero degrees with the optical axis.Graphs 11D and 12D show the performance of the optical assembly of FIG.8 for a ray bundle when the light source is moved providing an incidentangle of 15 degrees with the optical axis. Graphs 11C and 12C show theperformance of the optical assembly of FIG. 8 for a ray bundle when thelight source is moved providing an incident angle of 35 degrees with theoptical axis. Graphs 11B and 12B show the performance of the opticalassembly of FIG. 8 for a ray bundle when the light source is movedproviding an incident angle of 55 degrees with the optical axis. Graphs11A and 12A show the performance of the optical assembly of FIG. 8 for aray bundle when the light source is moved providing an incident angle of75 degrees with the optical axis.

LCA is demonstrated in FIGS. 11A-11E as the separation of the three rayswhich correspond to four different colors or wavelengths, which are inthis example 650 nm, 550 nm, 486 nm and 450 nm.

FIG. 13 illustrates the polychromatic diffraction modulation transferfunction (MTF) plots of contrast vs. spatial frequency for pixels lyingnormal to the optical axis (F1), 15 degrees from normal to the opticalaxis (F2), 35 degrees from normal to the optical axis (F3), 55 degreesfrom normal to the optical axis (F4), and 75 degrees from normal to theoptical axis (F5). Those pixels lying at 75 degrees from normal to theoptical axis would be those at the edge of a point action cameraassembly having a field of view of 150 degrees. A point action camera isprovided herein having a wide field of view of 150 degrees or more.Advantageously high areas under these curves are noticeable in FIG. 13.In accordance with FIGS. 11A-11E, the plots of FIG. 13 demonstrate thatthe image quality of the embodiment of FIG. 8 is advantageous.

FIG. 14 shows astigmatic field curves for tangential (e.g., vertical)fan (T) and sagittal (e.g., horizontal) fan (S) for the optical assemblyillustrated schematically at FIG. 8 as well as the tangential fan (T′)and sagittal fan (S′) for a similar optical assembly except that thethirteenth optical surface has no aspheric departure. FIG. 14 shows thatwithout the asphere, the longitudinal astigmatism (T′−S′)˜0.75 mm inthis example. With an aspheric departure in accordance with certainembodiments, e.g., on the thirteenth surface, such as has been describedand illustrated in the example of FIG. 8, the longitudinal astigmatismreduces to approximately zero. Moreover, the field curvature isapproximately flat, e.g., <50 microns, across the sensor format.

Both of the embodiments illustrated at FIGS. 1 and 8 exhibit ratios ofTTL/EFL that are less than 8. The embodiment of FIG. 8 has a ratio ofTTL/EFL that is less than 7.5, and may be approximately 7 orapproximately 7.4 or 7.43. The specific TTL/EFL ratios of 7.8 and 7.4for the specific non-limiting example embodiments illustrated at FIGS. 1and 8 are based on total track lengths typically between 18 and 21 andon effective focal lengths typically between 2.5 and 3.0. In certainembodiments, a ratio of TTL to EFL of 7.5 is achieved with a total tracklength of 20.3 and an effective focal length of 2.7. An effective focallength of the first group G1 that includes the first three lens elementsE1, E2 and E3 may be between approximately −120 and −60, or between −110and −70, or between −100 and −80, or approximately −90, or approximately−92 or −91.6. Among the lens elements of the first group G1, the firsttwo lens elements E1 and E2 may have a combined focal length between −1and −4, or between −1.5 and −3.5, or between −2 and −3, or around −2.5or −2 or −2.3, while the third element E3 may have a focal lengthbetween approximately +3 and +8, or between +4 and +7, or between +5 and+6, or around +5.5 or +5.3.

In this context, referring again to Table 4, which generally disclosescertain specifications of the example optical assembly that isrepresented schematically in side view in FIG. 8, Table 4 lists radiusof curvature (RDY) values for each of the fourteen optical surfaces,i.e., numbered 1-14 in the left hand column of Table 4, of the sevenlens elements E1-E7(A) that make up the first and second optical groupsG1, G2. Table 4 also lists thickness values (THI) for each of the lenselements and spacings between the lens elements, or of the distancesbetween each adjacent optical surface in the optical assemblyillustrated schematically in side view in FIG. 8. The optical assemblyof FIG. 8 has a TTL/EFL ratio of about 7.4, for a track length ofapproximately 20.3 mm and an effective focal length of approximately 2.7mm. The effective focal length of the lens group G1 is −91.6 mm and thatof the lens group G2 in this example is about 6.1 mm. The lens group G1could be broken down into the first two lenses E1 and E2 which togetherhave an effective (negative) focal length of about −2.3 mm, while thethird lens E3 has an effective (positive) focal length of about 5.3 mm.

Table 5 shows aspherical and spherical SAG data for the thirteenthsurface of the optical assembly of FIG. 8. These data may fit to aformula for SAG for a spherical conic section, e.g.,z(r)=r²/[R+(R²−r²)^(1/2)], wherein for a best sphere of radius 8.330, asin an example embodiment, and a curvature of best sphere, R,corresponding to 0.120047, the different actual radii of curvature, r,for a surface with aspheric departure produce SAG differences comparedto values for a true spherical conic section. These aspherical SAGs foran example thirteenth surface are compared with would be true sphericalSAGs in Table 5 for different distances Y from the vertex center at Y=0to Y=3.3 (mm) in steps of 0.132 (mm).

The aspheric sags in Table 6 that are plotted in FIG. 9 are the asphericsag difference numbers shown in Table 5, which are the differences fromthe best fit sphere sags of the aspheric surface 13. Table 6 also showsvalues of aspheric slope that are plotted in FIG. 10.

FIG. 9 is a plot of aspheric sag versus radial distance, or the dataprovided in the second column from the left in Table 6, for the 13^(th)optical surface from the object in the example optical assemblyillustrated schematically in FIG. 8. The aspheric sag for the 13^(th)surface in this example has a sag minimum between approximately −16 μmand −18 μm between 1.5 mm and 2.5 mm from the center of the 13^(th) lenssurface. The sag is approximately zero at the center and at the edgeabout 3 mm from the center. The sag plot has a width of approximately1.5 mm at −8.0 μm. The sag has points of inflection at approximately 1.0mm and 2.6 mm from the center of the 13^(th) lens surface.

FIG. 10 is a plot of slope of aspheric sag versus radial distance, orthe data provided in the fourth column from the left (or rightmostcolumn) in Table 6, for the 13^(th) optical surface in the exampleoptical assembly illustrated schematically in FIG. 8. The aspheric slopehas a minimum between −10 μm/mm and −15 μm/mm between 0.5 mm and 1.5 mmfrom the center of the 13^(th) lens surface. The aspheric slope has alargest value at the outer edge of the 13^(th) lens surface of between30 μm/mm and 40 μm/mm. The aspheric slope has points of inflection ataround 0.5 mm and between 2 mm and 2.5 mm from the center of the 13^(th)lens surface.

Certain embodiments include multiple lens elements that have one or bothsurfaces exhibiting some aspheric departure, including embodimentswherein each of the lens groups G1 and G2 (or G1 and G3 in the threelens group examples) has at least one aspheric lens element. However, anadvantage of both of the first and second example embodimentsillustrated schematically in FIGS. 1 and 8, respectively, involves easeof manufacturability compared with a design that might alternativelyhave an aspheric surface within both the first lens group G1 and thesecond lens group G2. For example, the first lens group G1 can becombined with the second lens group at any selected point in theprocess, and a versatile number of sources and optical alignment andassembly techniques may be available when only the single lens Group 2includes one or more aspheric surfaces. If one divides the opticalassembly into three lens groups G1 (including E1 and E2), G2 (includingE3) and G3 (including E4, E5/E6 and E7(A)) then further versatility inmanufacturing, alignment, assembly and optical application become morereadily available.

In a three lens group example in accordance with the first or secondembodiment, a focal length of group G1 may be negative and in certainembodiments between −1 mm and −5 mm and may be between −2 mm and −3 mm,and may be approximately −2 mm, −2.5 mm or −3 mm, for example, −2.3 mm.A focal length of group G2 (lens E3) may be positive and in certainembodiments between +3 mm and +8 mm, and may be between +4 mm and +7 mm,and may be between +5 mm and +6 mm, and may be approximately +5 mm, forexample, +5.3 mm. A focal length of group G3 may be positive and incertain embodiments less than +12 mm, and may be between +3 mm and +10mm, and may be between +4 and +8, and may be between +5 and +7, and maybe approximately 6 mm, e.g., +6.1 mm.

Third Example Embodiment

A third example embodiment is illustrated at FIGS. 15-21 and Tables 7-9,respectively, schematically and quantitatively. Like the first twoexample embodiments, the third example embodiment has a ratio of totaltrack length (TTL) to effective focal length (EFL) that is less than 8.The third example embodiment, like the first example embodiment,actually has a TTL/EFL ratio that is approximately 7, or that is betweenaround 7.0 and 7.8, or between around 7.2 and 7.6, or between around 7.3and 7.5 or approximately 7.4, or in a specific example, the ratio isaround 7.43. The third embodiment utilizes a different mix of opticalmaterials than either of the first and second embodiments. The basiclayout of the first and second optical groups G1 and G2 which areseparated by an aperture stop in FIG. 15 is configured to provide anadvantageously low distortion. The seventh lens element (from object toimage) E7 has at least one surface, e.g., the object facing surface orthirteenth surface of the optical system, that has an aspheric departurethat is configured to provide an advantageously low astigmatism erroracross the wide field of view of the optical assembly of the thirdexample embodiment illustrated schematically at FIG. 15.

In the third example embodiment, the lens element E7 may have aconvexo-planar or convexo-quasi-planar design as in the illustration ofFIG. 15. The 14^(th) optical surface of the lens assembly of FIG. 15 hasa flatter shape than the 14^(th) surface of the second embodiment. Inother embodiments, E7 may have a plano-convex or quasi-plano-convexdesign, wherein the fourteenth surface of the third example opticalassembly has an aspheric departure while the thirteenth surface doesnot. In certain embodiments, both the thirteenth and fourteenth surfaceshave aspheric departure.

In another embodiment, the 12^(th) surface or image facing surface ofthe lens element E6 has aspheric departure, while the 13^(th) and14^(th) surfaces may both be spherical without aspheric departure, ormay include one spherical surface and one planar or quasi-planar surfaceas in the illustration of FIG. 15, or may include one aspheric surface,or may both have significant aspheric departure. In other embodiments,the 1^(st), 2^(nd), 3^(rd) or 4^(th) lens surfaces of the opticalassembly may have aspheric departure such that the optical assemblyexhibits a wide field of view and both low distortion and lowastigmatism, while the 13th and 14th surfaces may both be sphericalwithout aspheric departure, or may include one spherical surface and oneplanar or quasi-planar surface as in the illustration of FIG. 15, or mayinclude one aspheric surface, or may both have significant asphericdeparture. In certain embodiments, only a single lens element of theoptical assembly has aspheric departure. One or both surfaces of thesingle aspheric lens element may have aspheric departure. The example ofFIG. 15 includes only a single aspheric lens surface, e.g., the 13^(th)surface or object facing surface of the seventh lens element E7(A). Incertain embodiments, only a single lens surface, e.g., the 1^(st),2^(nd), 3^(rd), 4^(th), 12^(th), 13^(th), or 14th has asphericdeparture. While any or all of the optical surfaces may have asphericdeparture in alternative embodiments, those lens surfaces that arenearest the image or object tend to provide the most significantcorrective capacities due to the greater differences between the chiefand marginal ray heights at those positions within the wide field ofview optical assembly of the third example embodiment.

A notable difference between the second and third example embodimentsillustrated schematically in side view at FIGS. 8 and 15, respectively,with regard to the shapes of the lenses and/or lens surfaces, has towith the third and fourth lens elements E3 and E4. The lens element E3of FIG. 16 has a thicker biconvex shape than that illustratedschematically in FIG. 8. The lens element E4 of FIG. 15 has a meniscusshape that is concavo-convex or quasi-planar (slightly concave)-convexcompared with the biconvex or quasi-planar (slightly convex)-convexdesign of the fourth lens element E4 of the example illustrated at FIG.8.

The first lens group G1 of the third example embodiment of FIG. 15includes two convexo-concave meniscus collecting lenses E1 and E2 andthe third biconvex converging lens E3. The lens elements E4 through E7of the second lens group G2 include, from nearest to aperture stop tonearest to image plane, the quasi-plano-convex meniscus lens E4, thedoublet E5/E6 including a plano-concave lens E5 and a biconvex lens E6that are substantially in contact at the 10^(th) and 11^(th) surfaces ofthe optical assembly of FIG. 15, and the aspheric lens element E7(A).The aspheric lens element E7(A) has a convexo-planar orconvexo-quasi-planar shape in this third example embodiment, while inthe second example embodiment illustrated schematically in side view atFIG. 8 the lens element E7(A) has a biconvex design, or aconvexo-quasi-planar shape wherein the 14^(th) lens surface is flatterin the third example of FIG. 15 than in the second example of FIG. 8even when in certain embodiments both can be termedconvexo-quasi-planar.

There is a significant advantage to the location of the doublet E5/E6between the lenses E4 and E7. Specifically, this location facilitatesthe correction of oblique aberrations. In alternative embodiments, thedoublet is disposed on the image side of the aperture stop between E3and E4, or in other embodiments on the object side of the aperture stop.In this embodiment, the lens element E7(A) is a plano-convex asphere,wherein S1 is aspheric and S2 is plano (wherein S1 and S2 are in thisexample the 13^(th) and 14^(th) optical surfaces of the lens assemblyillustrated in FIG. 15).

The first two lenses E1 and E2 together have a negative focal lengththat may be between around −1 and −5, or between approximately −1.5 and−3.5 or −4, or between around −2 and −3, or about −2.5 or −2.6. thethird lens E3 may have a positive focal length between +5 and +15, orbetween around +7 and +12, or between around +8 and +11, or about +9, or+9.2 or +9.3. The final four lenses, or the lens group G2, may have acombined positive focal length between +1 and +10, or between around +2and +7, or between around +3 and +6, or between around +4 and +5, orapproximately +4.5, or +4.7. The optical assembly illustratedschematically in FIG. 15 may have a ratio of total track length (TTL) toeffective focal length (EFL) that is less than 8, or between 5 and 10,or between approximately 6 or 7 and 8 or 9, or between 7.2 and 7.7, orbetween 7.3 and 7.6, or between 7.4 and 7.5, or around 7.4 or 7.43. TheTTL may be between 15 mm and 25 mm, or between 17 mm and 23 mm, orbetween 18 mm and 22 mm, or between 19 mm and 21 mm, or around 20 mm or20.3 mm. The EFL may be between approximately 1.5 mm and 5 mm, orbetween about 2 m and 3.5 mm or 4 mm, or between around 2.5 mm and 3 mm,or between around 2.7 mm and 2.8 mm, or around 2.73 mm.

Table 7 provides quantitative data for the third example embodiment.FIGS. 17-22 illustrate advantageous features of the optical assemblyshown in schematic side view representation at FIG. 15. Table 8 showsaspherical and spherical SAG data for the thirteenth surface of theoptical assembly of FIG. 15. These data may fit to a formula for SAG fora spherical conic section, e.g., z(r)=r²/[R+(R²−r²)^(1/2)], wherein fora best sphere of radius 8.330, as in an example embodiment, and acurvature of best sphere, R, corresponding to 0.120047, the differentactual radii of curvature, r, for a surface with aspheric departureproduce SAG differences compared to values for a true spherical conicsection. These aspherical SAGs for an example thirteenth surface arecompared with would be true spherical SAGs in Table 8 for differentdistances Y from the vertex center at Y=0 to Y=3.3 (mm) in steps of0.132 (mm).

The aspheric sags in Table 9 that are plotted in FIG. 16 are theaspheric sag difference numbers shown in Table 8, which are thedifferences from the best fit sphere sags of the aspheric surface 13.Table 9 also shows values of aspheric slope that are plotted in FIG. 17.

FIG. 16 is a plot of aspheric sag versus radial distance, or the dataprovided in the second column from the left in Table 9, for the 13^(th)optical surface from the object in the example optical assemblyillustrated schematically in FIG. 15. The aspheric sag for the 13^(th)surface in this example has a sag minimum between approximately −5 μmand −6 μm between 1.5 mm and 2 mm from the center of the 13^(th) lenssurface. The sag is approximately zero at the center and is about −1 μmat the edge about 3 mm from the center. The sag plot has a width ofapproximately 1.5 mm at −3.0 μm. The sag has points of inflection atapproximately 1.0 mm and 2.5 mm from the center of the 13^(th) lenssurface.

FIG. 17 is a plot of slope of aspheric sag versus radial distance, orthe data provided in the fourth column from the left (or rightmostcolumn) in Table 9, for the 13^(th) optical surface in the exampleoptical assembly illustrated schematically in FIG. 15. The asphericslope has a minimum between −4 μm/mm and −6 μm/mm at about 1 mm from thecenter of the 13^(th) lens surface. The aspheric slope has a maximumnear the outer edge of the 13^(th) lens surface around 2.5 mm from thecenter of between 6 μm/mm and 8 μm/mm. The aspheric slope has points ofinflection at around 0.5 mm and 2 mm from the center of the 13^(th) lenssurface.

FIGS. 18A-18E respectively show plots of tangential ray aberrationsrespectively at 75°, 55°, 35°, 15° and 0° for the wide field of viewobjective assembly illustrated in FIG. 15. FIGS. 18A-18E and 19A-19Eshow five pairs of graphs, where each pair illustrates the tangentialand sagittal rays at one of these five field angles. The independentvariable (horizontal axis) is the relative coordinate of a ray over thepupil diameter. The vertical axis has a maximum distance measure of+/−approximately three microns or a spread of six microns or less over a150 degree field (which is clearly advantageous over a conventionalsystem that may have, e.g., a 20 micron spread. The vertical axistherefore represents the transverse ray aberration (ray interceptiondistance from the ideal focal point) of a ray passing through a specificrelative pupil position. Graphs 18A-18E (tangential plane) and 19A-19E(sagittal plane) show the transverse ray aberrations for an on-axis raybundle as the bundle is refracted through the lens elements of theoptical assembly of FIG. 15.

In FIGS. 18E and 19E, the performance of the embodiment of FIG. 15 isillustrated for a ray bundle at zero degrees with the optical axis.Graphs 18D and 19D show the performance of the optical assembly of FIG.15 for a ray bundle when the light source is moved providing an incidentangle of 15 degrees with the optical axis. Graphs 18C and 19C show theperformance of the optical assembly of FIG. 1 for a ray bundle when thelight source is moved providing an incident angle of 35 degrees with theoptical axis. Graphs 18B and 19B show the performance of the opticalassembly of FIG. 15 for a ray bundle when the light source is movedproviding an incident angle of 55 degrees with the optical axis. Graphs18A and 19A show the performance of the optical assembly of FIG. 15 fora ray bundle when the light source is moved providing an incident angleof 75 degrees with the optical axis.

LCA is demonstrated in FIGS. 18A-18E as the separation of the three rayswhich correspond to four different colors or wavelengths, which are inthis example 650 nm, 550 nm, 486 nm and 450 nm.

FIG. 20 illustrates the polychromatic diffraction modulation transferfunction (MTF) plots of contrast vs. spatial frequency for pixels lyingnormal to the optical axis (F1), 15 degrees from normal to the opticalaxis (F2), 35 degrees from normal to the optical axis (F3), 55 degreesfrom normal to the optical axis (F4), and 75 degrees from normal to theoptical axis (F5). Those pixels lying at 75 degrees from normal to theoptical axis would be those at the edge of a point action cameraassembly having a field of view of 150 degrees. A point action camera isprovided herein having a wide field of view of 150 degrees or more.Advantageously high areas under these curves are noticeable in FIG. 20.In accordance with FIGS. 18A-18E, the plots of FIG. 20 demonstrate thatthe image quality of the embodiment of FIG. 15 is advantageous.

FIG. 21 shows astigmatic field curves for tangential (e.g., vertical)fan (T) and sagittal (e.g., horizontal) fan (S) for the optical assemblyillustrated schematically at FIG. 15 as well as the tangential fan (T′)and sagittal fan (S′) for a similar optical assembly except that thethirteenth optical surface has no aspheric departure. FIG. 21 shows thatwithout the asphere, the residual field curvature ˜0.25 mm in thisexample. With an aspheric departure in accordance with certainembodiments, e.g., on the thirteenth surface, such as has been describedand illustrated in the example of FIG. 15, the longitudinal astigmatismreduces to less than 0.05 mm. That is, the field curvature isapproximately flat, e.g., <50 microns, across the sensor format.

Fourth Example Embodiment

FIG. 22 schematically illustrates another optical assembly for a pointaction camera in accordance with certain embodiments. The opticalassembly of FIG. 22 includes a first optical group G1 and a secondoptical group G2 that are configured to provide a wide field of viewwith low distortion compared with conventional wide field of viewsystems. An advantageous bi-aspheric lens element is provided to correctastigmatism across the wide field of view, e.g., >150°. Certainembodiments of the optical assembly according to the example illustratedat FIG. 22 include a single bi-aspheric lens element. In certainembodiments, the single bi-aspheric lens element is the only lenselement of the lens elements of the optical assembly that has anon-negligible aspheric departure on either surface.

In certain embodiments of the optical assembly having a singlebi-aspheric lens element, the field curvature is less than 75 microns,and a subset of these embodiments provides field curvatures that areless than 60 microns, and another subset provides images that exhibitfield curvatures that are less than 50 microns. Certain subsets ofembodiments have astigmatism across the wide field of view that is lessthan 7 mm, 5 mm, 3 mm, 2 mm and 1 mm. In certain embodiments, the ratioof total track length to effective focal length is less than 8.

Referring now to FIG. 22, The signs of the curvatures of the lenselements in the illustrative example are similar to those describedabove with reference to any of FIG. 1, 8 or 15, or combinations thereof,such that the above discussions are incorporated rather than repeatedhere. The position of the single bi-aspheric lens element may be as theultimate or penultimate lens element on the image side or on the objectside of the optical assembly, e.g., at E1, E2, E6 or E7, as the enhancedchief ray to marginal ray distances improve the versatility inastigmatism compensation performance of the bi-aspheric lens element. Insingle-aspheric lens element is selected in the example illustrated atFIG. 22 as the seventh and ultimate lens element labeled E7(A)(A) fromobject to image of the wide field of view optical assembly.

The lens assembly illustrated at FIG. 22 includes a doublet, whereby inthis example, the 10^(th) and 11^(th) surfaces are not spaced apart butare instead combined together. The doublet E5/E6 advantageouslyfacilitates the correction of oblique aberrations that may otherwise bepresent without the doublet E5/E6.

An aperture stop is provided between the lens groups G1 and G2, orbetween the third biconvex, or quasi-plano-convex or convexo-quasi-planolens element E3 and the concavo-convex meniscus, biconvex, plano orquasi-plano convex lens element E4. One or more further apertures may beincluded in certain alternative embodiments.

The first two convexo-concave collecting lens elements E1 and E2 mayhave an effective focal length between around −1 mm and −4 mm, orbetween around −1.5 mm and −3.5 mm, or between around −2 mm and −3 mm,or approximately-2.4 mm or −2.5 mm or −2.46 mm. The effective focallength of the lens element E3 may be between 4 mm and 12 mm, or between5 mm and 11 mm, or between 6 mm and 10 mm, or between 7 mm and 9 mm, orapproximately 8.1 mm. The overall effective focal length o the group G1including lens elements E1, E2 and E3 may be between 1 mm and 5 mm, orbetween 1 mm and 4 mm, or between 1.5 mm nd 3.5 mm, or between 2 mm and3 mm, or between around 2.7 mm and 2.8 mm, or approximately 2.73 mm. theeffective focal length of the second lend group G2 including lenselements E4, E5/E6 and E7(A)(A) in the example illustrated schematicallyin side view at FIG. 22 may be between 2 mm and 7 mm, or between 3 mmand 6 mm, or between 4 mm and 5 mm, or between 4.5 mm and 4.8 mm, orbetween 4.6 mm and 4.7 mm, or approximately 4.64 mm.

The ratio of total track length to effective focal length in thisexample may be less than 8, or approximately 7 or 7.5, or between 7 and8, or less than about 7.8, 7.7, 7.6 or 7.5. The total track length maybe approximately 20.5 mm and the effective focal length approximately2.7 mm.

Table 10 provides a quantitative optical prescription of the surfaces ofthe optical elements of an optical assembly in accordance with oneexample of the system that is illustrated schematically at FIG. 22. Theleft most column indicates the number of the surface from the object tothe image. The second column from the left indicates the radius ofcurvature of the surface. The third column from the left indicates thethickness or distance from the surface to the next surface travelling ina direction from object to image. The rightmost column indicates theindex of refraction and the dispersion of the material selected for eachoptical element in this example.

The indices of refraction for the lens elements E1-E7(A)(A) areindicated in Table 10 as 1.73, 1.73, 1.92, 1.62, 1.92, 1.62, and 1.5,respectively, while the indices of refraction of the IR cut filter andthe cover glass for the image sensor are each indicated as 1.52. Thedispersion of the lens elements E1-E7(A)(A) are indicated in Table 10 as55, 55, 19, 63, 19, 63 and 82, respectively, while the dispersion of theIR cut filter and cover glass are each indicated as 64.

The aspheric constants or coefficients A, B, C and D for the 13^(th) and14^(th) surfaces, respectively, may be inserted into the asphericequation provided at the top of each of Tables 11 and 12 to obtain aformula that describes the aspheric curvatures of these 13^(th) and14^(th) surfaces in this example.

In a fourth example embodiment, another optical assembly for a pointaction camera is configured for capturing images with a wide field ofview and includes a single aspheric lens element, wherein the singleaspheric lens element may be a bi-aspheric lens element, i.e., havingtwo aspheric surfaces. In the fourth example embodiment, the opticalassembly includes two or three optical groups as described with respectto the first, second and third example embodiments, e.g., includingfour, five, six or seven or more lens elements. In a seven lens elementexample, the seventh lens element is the only lens element having asignificant aspheric departure. Each of the first through sixth lenselements in this example, from object to image, include approximatelyspherical surfaces within optical tolerances, while the seventh lenselement has both an aspheric object facing surface and an aspheric imagefacing surface. The overall design is configured to capture wide fieldof view images, e.g., exceeding 90 degrees, 120 degrees, 135 degrees,150 degrees and in certain embodiment even 180 degrees or more withtolerable distortion characteristics. The aspheric departures of the13^(th) and 14^(th) lens surfaces are configured to correct astigmatismerror that would otherwise be present in the design.

Tables 11-12 and 13-14, respectively, show data for example asphericdepartures for the 13^(th) and 14^(th) lens surfaces of a seventh lenselement of a wide field of view optical assembly in accordance withcertain embodiments that includes a single aspheric lens element. Inthis example, the radius of the seventh lens element is approximatelyjust below 3 mm, and aspheric sags and sag slopes are indicated at radiifrom the center Y=0 in the Tables 11-14 in steps of 115 microns out toY=2.875.

The second and third columns from the left in each of Tables 11-12 showthe data for aspherical and spherical sags, respectively, for the13^(th) and 14^(th) surfaces, respectively. The fourth column from leftin Tables 11-12 show the data for aspheric sag of the 13^(th) and14^(th) surfaces, respectively, as a distance between a plane normal tothe optical axis that would include a point along the optical surface atthe radius provided in the left-most column and a parallel plane thatactually includes the point along the optical surface at that radius.The sag differences indicated in the fourth column from the left inTables 11-12 manifest the aspheric departures of the 13^(th) and 14^(th)surfaces, respectively, from a best fit sphere. The data for the slopeof the sags provided in the fourth column, or the derivative of the sagslope with respect to radius or height Y for the 13^(th) and 14^(th)surfaces in this example, are respectively provided in the Table 13-14.

FIG. 23 is a plot of aspheric sag versus radial distance, or the dataprovided in the fourth column from the left in Table 10, for the 13^(th)optical surface from the object in the example optical assemblyillustrated schematically in FIG. 22. The aspheric sag for the 13^(th)surface in this example has a sag between approximately −5 μm and −6 μmat the center and at its outermost edge around 3 mm from the center ofthe 13^(th) lens surface. The sag is less than −5 everywhere between 0.5mm and 2.5 mm from the center. The sag plot has a width of approximately1.5 mm at −3.0 μm. The sag has a maximum of 0 μm between 1.5 mm and 2.0mm from the center. In one embodiment, the maximum sag is at 1.8 mm. Asag minimum is shown in FIG. 23 between 2.5 mm and 3.0 mm ofapproximately −6 μm. In one embodiment, the minimum sag is at a radialdistance of about 2.8 mm from the center of the 13^(th) lens surface.The sag has points of inflection at approximately 1.0 mm and 2.3 mm fromthe center of the 13^(th) lens surface.

FIG. 24 is a plot of slope of aspheric sag versus radial distance, orthe data provided in the fifth column from the left in Table 10, for the13^(th) optical surface in the example optical assembly illustratedschematically in FIG. 22. The aspheric slope has a maximum between 4μm/mm and 5 μm/mm between 1.0 mm and 1.5 mm from the center of the13^(th) lens surface. The aspheric slope has a minimum of −10 μm/mm at2.5 mm from the center of the 13^(th) lens surface. The aspheric sloperises to about 6 μm/mm from 2.5 mm to the outer edge. The aspheric slopehas points of inflection at around 0.5 mm and 2 mm from the center ofthe 13^(th) lens surface.

The second and third columns from the left in Table 11 show the data foraspherical and spherical sags, respectively, for the 14^(th) surface.The fourth column from left shows the data for aspheric sag of the14^(th) surface as a distance between a plane normal to the optical axisthat would include a point along the 14^(th) optical surface at theradius provided in the left-most column and a parallel plane thatactually includes the point along the 14^(th) surface at that radius.The sag differences indicated in the fourth column from the left inTable 11 manifest the aspheric departure of the 14^(th) surface from abest fit sphere. The data for the slope of the sags provided in thefourth column, or the derivative of the sag slope with respect to radiusor height Y for the 14th surface in this example, are provided in thefifth column from the left in Table 11.

FIG. 25 is a plot of aspheric sag versus radial distance, or the dataprovided in the fourth column from the left in Table 11, for the 14^(th)optical surface from the object, in the example optical assemblyillustrated schematically in FIG. 22. The aspheric sag for the 14^(th)surface in this example has a sag of approximately 0 μm at the centerand at its outermost edge around 3 mm from the center of the 14^(th)lens surface. The sag is positive everywhere between the center and theedge. The sag plot has a width of approximately 1.5 mm at 14 μm. The saghas a maximum of 28 μm at approximately 2 mm from the center. The saghas points of inflection between approximately 1.0 mm and 1.5 mm andbetween approximately 2.5 mm and 3 mm from the center of the 14^(th)lens surface.

FIG. 26 is a plot of slope of aspheric sag versus radial distance, orthe data provided in the fifth column from the left in Table 11, for the14^(th) optical surface from the object, in the example optical assemblyillustrated schematically in FIG. 22. The aspheric slope has a maximumjust above 20 μm/mm between 1.0 mm and 1.5 mm from the center of the14^(th) lens surface. The aspheric slope has a minimum between −40 μm/mmand −50 μm/mm near the outermost edge of the 14^(th) lens surface. Theaspheric slope has points of inflection between around 0.5 mm and 1 mmand between 2 mm and 2.5 mm from the center of the 14^(th) lens surface.

FIGS. 27A-27E and 28A-28E respectively show plots of tangential andsagittal ray aberrations for the wide field of view objective assemblyillustrated in FIG. 22.

FIG. 29 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 22 normal to the opticalaxis (F1), 15 degrees from normal to the optical axis (F2), 35 degreesfrom normal to the optical axis (F3), 55 degrees from normal to theoptical axis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 30 shows astigmatic field curves for tangential fan (T) andsagittal fan (S) for the optical assembly illustrated schematically atFIG. 22 as well as the tangential fan (T′) and sagittal fan (S′) for asimilar optical assembly except that the thirteenth optical surface hasno aspheric departure.

General Discussion

Yet greater dynamic capacities in the process of building a point actioncamera with both wide field of view and heretofore unknown reduction indistortion, astigmatism and combinations of these optical aberrationsthat have been otherwise problematic in conventional wide field of viewsystems is provided herein with optical assemblies in accordance withmultiple embodiments that contain only one aspheric lens element, e.g,lens element E1 or E2 of the first lens group G1 or lens element E5/E6,E6 or E7 of the lens group G2 in combination with five or six lenselements that have spherical curvatures to understood tolerances. One orboth surfaces of the single aspheric lens element of these embodimentsmay have significant calculated aspheric departure, while the other lenselements are spheres (or in other embodiments cylinders or a combinationof cylinders and spheres).

Example embodiments have been provided above wherein only one opticalsurface within the optical assembly has a specifically-intended andadvantageous aspheric departure. In the embodiments illustratedschematically in side view in FIGS. 1 and 9, five or six lens elements,depending on how the E5/E6 doublet is characterized, do not havedepartures from spherical (i.e., at least none that exceed specifiedoptical tolerances).

In another set of embodiments, one or more aspheric lens element is/areprovided in the first lens Group G1. For example, lens element E1 and/orE2 may have one or more surfaces with aspheric departures that serve toreduce astigmatism in a wide field of view point action camera systemthat is also or already configured with significantly reduced distortioncharacteristics, particularly at the edges of the field of view (e.g.,50°, 55°, 60°, 65°, 70°, or 75° or more from normal to the opticalaxis), where conventional uncorrected wide field of view systems tend toexhibit unacceptably high combinations of either or both of distortionaland astigmatic aberrations. In certain embodiments, only lens element E1or lens element E2 has one or both surfaces that exhibit calculablyadvantageous aspheric departures.

In specific embodiments, only a single surface, e.g., the 1^(st),2^(nd), 3^(rd) or 4^(th) surface, of the optical assembly has asphericdeparture that provides a point action camera with a wide field of viewalong with unprecedented reductions in distortional, astigmatic orcombinational aberrations that would be otherwise inherent in lessthorough designs, in designs without any aspheric surface or surfacesand/or in designs without the specific optical design shape and/oraberrational error correctional characteristics provided herein. In aspecific alternative embodiment, only the first lens surface of theoptical assembly, or the surface of lens E1 that faces the object,includes demonstratedly and advantageously significant asphericdeparture. In another embodiment, the image facing surface of lens E1has a uniquely aspherical attributional curvature characteristic withinthe optical assembly of a wide field of view point action camera.

Alternative embodiments have a single aspheric surface within the lensgroup G2 at the twelfth lens surface or image facing surface of the lensE6 (or E6(A) in this alternative embodiment) which is the image-sidelens of the doublet E5/E6. Another alternative to having asphericdeparture on the thirteenth surface (as in the above illustratedexamples) is to instead provide aspheric curvature on the fourteenthlens surface, which is the image facing surface of the lens E7(A). Othersurfaces of the lens group G2 such as the seventh through eleventhsurfaces of the optical assemblies illustrated in FIGS. 1 and 9 couldalso have aspheric departures that could benefit, albeit to a lesserextent than the aforementioned 12^(th), 13^(th) and/or 14^(th) opticalsurfaces of lens group G2, the versatility and optical designcharacteristics of an optical assembly of a point action camera.

While an exemplary drawings and specific embodiments of the presentinvention have been described and illustrated, it is to be understoodthat that the scope of the present invention is not to be limited to theparticular embodiments discussed. Thus, the embodiments shall beregarded as illustrative rather than restrictive, and it should beunderstood that variations may be made in those embodiments by workersskilled in the arts without departing from the scope of the presentinvention.

In addition, in methods that may be performed according to preferredembodiments herein and that may have been described above, theoperations have been described in selected typographical sequences.However, the sequences have been selected and so ordered fortypographical convenience and are not intended to imply any particularorder for performing the operations, except for those where a particularorder may be expressly set forth or where those of ordinary skill in theart may deem a particular order to be necessary.

A group of items linked with the conjunction “and” in the abovespecification should not be read as requiring that each and every one ofthose items be present in the grouping in accordance with allembodiments of that grouping, as various embodiments will have one ormore of those elements replaced with one or more others. Furthermore,although items, elements or components of the invention may be describedor claimed in the singular, the plural is contemplated to be within thescope thereof unless limitation to the singular is explicitly stated orclearly understood as necessary by those of ordinary skill in the art.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other such as phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “assembly” does not imply that the components or functionalitydescribed or claimed as part of the assembly are all configured in acommon package. Indeed, any or all of the various components of aassembly, e.g., optical group 1 and optical group 2, may be combined ina single package or separately maintained and may further bemanufactured, assembled or distributed at or through multiple locations.

Different materials may be used to form the lenses of the opticalassemblies of the several embodiments. For example, various kinds ofglass and/or transparent plastic or polymeric materials may be used.Examples include polyimides. Among the polymeric materials are highrefractive index polymers, or HRIPs, with refractive indices typicallyabove 1.5 (see, e.g., Hung-Ju Yen and Guey-Sheng Liou (2010). “A facileapproach towards optically isotropic, colorless, and thermoplasticpolyimidothioethers with high refractive index”. J. Mater. Chem. 20(20): 4080; H. Althues, J. Henle and S. Kaskel (2007). “Functionalinorganic nanofillers for transparent polymers”. Chem. Soc. Rev. 9 (49):1454-65; Akhmad Herman Yuwono, Binghai Liu, Junmin Xue, John Wang,Hendry Izaac Elim, Wei Ji, Ying Li and Timothy John White (2004).“Controlling the crystallinity and nonlinear optical properties oftransparent TiO2-PMMA nanohybrids”. J. Mater. Chem. 14 (20): 2978;Naoaki Suzuki, Yasuo Tomita, Kentaroh Ohmori, Motohiko Hidaka andKatsumi Chikama (2006). “Highly transparent ZrO2 nanoparticle-dispersedacrylate photopolymers for volume holographic recording”. Opt. Express14 (26): 012712, which are incorporated by reference).

Optical image stabilization techniques may be included in a point actioncamera in accordance with certain embodiments. For examples, techniquesdescribed at U.S. Pat. Nos. 8,649,628, 8,649,627, 8,417,055, 8,351,726,8,264,576, 8,212,882, 8,593,542, 8,509,496, 8,363,085, 8,330,831,8,648,959, 8,637,961, 8,587,666, 8,604,663, 8,521,017, 8,508,652,8,358,925, 8,264,576, 8,199,222, 8,135,184 and 8,184,967, and USpublished patent applications nos. 2012/0121243, 2012/0207347,2012/0206618, 2013/0258140, 2013/0201392, 2013/0077945, 2013/0076919,2013/0070126, 2012/0019613, 2012/0120283, and 2013/0075237 which arehereby incorporated by reference, may be used.

Additionally, the various embodiments set forth herein are described interms of exemplary schematic diagrams and other illustrations. As willbe apparent to one of ordinary skill in the art after reading thisdocument, the illustrated embodiments and their various alternatives maybe implemented without confinement to the illustrated examples. Forexample, schematic diagrams and their accompanying description shouldnot be construed as mandating a particular architecture orconfiguration.

Point action cameras in accordance with several further embodiments aredescribed herein. Several examples of point action cameras that can beefficiently manufactured are illustrated in the text with reference toaccompanying drawings. Certain optical parts of the point action camerasuch as one or more lenses, mirrors and/or apertures, a shutter, ahousing or barrel for holding certain optics, a lens or a lens barrel,or other optic such as a mirror, light source, secondary sensor,accelerometer, gyroscope, power connection, a data storage chip, amicroprocessor, a wired or wireless transmission/reception connectionand/or receiver/transmitter, or housing alignment and/or coupling pinsor recesses or other such structures may be included in certainembodiments even if they have not been specifically described orillustrated herein. It is noted that in certain embodiments, a shutteris included, while in other embodiments, the point action camera doesnot have a shutter. A flash may or may not be included in any of thesecamera embodiments.

In certain embodiments, a wide field of view is desired in only a singledimension. In such cases, the principles described herein can be reducedto cylindrical applications of any of the spherical examples provided.

In addition, all references cited above and below herein, as well as thebackground, invention summary, abstract and brief description of thedrawings, are all incorporated by reference into the detaileddescription of the preferred embodiments as disclosing alternativeembodiments. Several embodiments of point action cameras have beendescribed herein and schematically illustrated by way of examplephysical, electronic and optical architectures. Other point actioncamera embodiments and embodiments of features and components of pointaction cameras that may be included within alternative embodiments, maybe described at one or a combination of U.S. Pat. Nos. 7,224,056,7,683,468, 7,936,062, 7,935,568, 7,927,070, 7,858,445, 7,807,508,7,569,424, 7,449,779, 7,443,597, 7,449,779, 7,768,574, 7,593,636,7,566,853, 7,858,445, 7,936,062, 8,005,268, 8,014,662, 8,090,252,8,004,780, 8,119,516, 7,920,163, 7,747,155, 7,368,695, 7,095,054,6,888,168, 6,844,991, 6,583,444, and/or 5,882,221, and/or US publishedpatent applications nos. 2013/0270419, 2013/0258140, 2014/0028887,2014/0043525, 2012/0063761, 2011/0317013, 2011/0255182, 2011/0274423,2010/0053407, 2009/0212381, 2009/0023249, 2008/0296717, 2008/0099907,2008/0099900, 2008/0029879, 2007/0190747, 2007/0190691, 2007/0145564,2007/0138644, 2007/0096312, 2007/0096311, 2007/0096295, 2005/0095835,2005/0087861, 2005/0085016, 2005/0082654, 2005/0082653, and/or2005/0067688. All of these patents and published patent applications areincorporated by reference.

U.S. Pat. Nos. 7,593,636, 7,768,574, 7,807,508 and 7,244,056 which areincorporated by reference describe examples of structures where theelectrical height of a camera device is nested within the optical heightto decrease the physical height. An advantageously compact point actioncamera is provided herein in alternative embodiments. Point actioncameras that have an advantageously low ratio of optical length (orphysical size or height) to effective focal length, or TTL/EFL, areprovided herein. In specifically described examples, optical assemblieswith TTL/EFL ratios below 8.0 are provided.

US2013/0242080 which is also incorporated by reference describesexamples of point action cameras or camera modules disposed withinwatertight compartments. A mechanism may be provided for optical and/orelectrical communication of image data that does not involve breakingthe watertight seal of the housing within which the point action cameraresides.

What is claimed is:
 1. An optical assembly for a point action camerahaving a wide field of view, comprising multiple lens elements includingan aspheric surface, configured to provide a field of view in excess of150 degrees that comprises an inward field curvature of less than 75microns, wherein the optical assembly comprises from object end to imageend a first optical group and a second optical group, wherein the firstoptical group is configured to collect light at said wide field of viewand said second optical group is configured to compensate for distortionand astigmatism error, and wherein said second optical group comprisesmultiple lens elements including an ultimate or penultimate lens elementthat is configured with an aspheric departure to compensate for saidastigmatism error, and wherein said optical assembly comprises sevenlens elements; wherein said optical assembly comprises a third opticalgroup disposed between the first and second optical groups, and whereinthe third optical group comprises a biconvex lens.
 2. The opticalassembly of claim 1, wherein the inward field curvature comprises lessthan 60 microns.
 3. The optical assembly of claim 1, wherein the inwardfield curvature comprises approximately 50 microns or less.
 4. Theoptical assembly of claim 1, wherein the optical assembly has alongitudinal astigmatism that comprises approximately 0.7 mm or less. 5.The optical assembly of claim 1, wherein the optical assembly has alongitudinal astigmatism that comprises approximately 0.5 mm or less. 6.The optical assembly of claim 1, wherein the optical assembly has alongitudinal astigmatism that comprises approximately 0.3 mm or less. 7.The optical assembly of claim 1, wherein the optical assembly has alongitudinal astigmatism that approximately 0.2 mm or less.
 8. Theoptical assembly of claim 1, wherein the optical assembly has alongitudinal astigmatism that comprises approximately 0.1 mm or less. 9.The optical assembly of claim 1, comprising an aperture stop betweensaid first and second optical groups.
 10. The optical assembly of claim1, wherein said ultimate lens element comprises an aspheric lenssurface.
 11. The optical assembly of claim 10, wherein said ultimatelens element comprises an object facing side and an image facing side,and wherein said object facing side comprises said aspheric departure.12. The optical assembly of claim 11, wherein the image facing side ofsaid ultimate lens element comprises an aspheric lens surface.
 13. Theoptical assembly of claim 10, wherein said ultimate lens elementcomprises an object facing side and an image facing side, and whereinsaid image facing side comprises said aspheric departure.
 14. Theoptical assembly of claim 1, wherein said second optical group comprisesfour lens elements.
 15. The optical assembly of claim 1, wherein saidsecond optical group comprises from object side to image side, a firstsinglet, a doublet and a second singlet.
 16. The optical assembly ofclaim 15, wherein said first singlet comprises a biconvex orplano-convex or quasi-plano-convex lens.
 17. The optical assembly ofclaim 16, wherein said second singlet comprises a biconvex, orconvexo-plano or convexo-quasi-plano lens.
 18. The optical assembly ofclaim 17, wherein said first optical group comprises two or moreconvexo-concave or meniscus lenses.
 19. The optical assembly of claim16, wherein said doublet comprises, from object side to image side, abiconcave lens and a biconvex lens.
 20. The optical assembly of claim 1,wherein the lateral chromatic aberration is less than approximatelythree pixels.
 21. The optical assembly of claim 1, wherein the lateralchromatic aberration is less than approximately two pixels.
 22. Theoptical assembly of claim 1, wherein the lateral chromatic aberration isless than approximately five microns.
 23. The optical assembly of claim1, wherein the lateral chromatic aberration is less than approximatelythree microns.
 24. A digital camera, comprising an optical assembly asin claim 1; and an image sensor disposed approximately at a focal planeof the optical assembly; and a digital camera housing includingelectronics and a user interface, and containing said optical assemblyand said image sensor in optically effective relative disposition. 25.The digital camera of claim 24, wherein the inward field curvaturecomprises less than 60 microns.
 26. The digital camera of claim 24,wherein the inward field curvature comprises approximately 50 microns orless.
 27. The digital camera of claim 24, wherein the optical assemblyhas a longitudinal astigmatism that comprises approximately 0.7 mm orless.
 28. The digital camera of claim 24, wherein the optical assemblyhas a longitudinal astigmatism that comprises approximately 0.5 mm orless.
 29. The digital camera of claim 24, wherein the optical assemblyhas a longitudinal astigmatism that comprises approximately 0.3 mm orless.
 30. The digital camera of claim 24, wherein the optical assemblyhas a longitudinal astigmatism that approximately 0.2 mm or less. 31.The digital camera of claim 24, wherein the optical assembly has alongitudinal astigmatism that comprises approximately 0.1 mm or less.32. The digital camera of claim 24, comprising an aperture stop betweensaid first and second optical groups.
 33. The digital camera of claim32, wherein said ultimate lens element comprises said asphericdeparture.
 34. The digital camera of claim 33, wherein said ultimatelens element comprises an object facing side and an image facing side,and wherein said object facing side comprises said aspheric departure.35. The optical assembly of claim 34, wherein the image facing side ofsaid ultimate lens element comprises an aspheric lens surface.
 36. Theoptical assembly of claim 33, wherein said ultimate lens elementcomprises an object facing side and an image facing side, and whereinsaid image facing side comprises said aspheric departure.
 37. Thedigital camera of claim 24, wherein said second optical group comprisesfour lens elements.
 38. The digital camera of claim 37, wherein saidsecond optical group comprises from object side to image side, a firstsinglet, a doublet and a second singlet.
 39. The digital camera of claim38, wherein said first singlet comprises a biconvex or plano-convex orquasi-plano-convex lens.
 40. The digital camera of claim 39, whereinsaid second singlet comprises a biconvex, or convexo-plano orconvexo-quasi-plano lens.
 41. The digital camera of claim 40, whereinsaid first optical group comprises two or more convexo-concave ormeniscus lenses.
 42. The digital camera of claim 38, wherein saiddoublet comprises, from object side to image side, a biconcave lens anda biconvex lens.
 43. The digital camera of claim 24, wherein the lateralchromatic aberration is less than approximately three pixels.
 44. Thedigital camera of claim 24, wherein the lateral chromatic aberration isless than approximately two pixels.
 45. The digital camera of claim 24,wherein the lateral chromatic aberration is less than approximately fivemicrons.
 46. The digital camera of claim 24, wherein the lateralchromatic aberration is less than approximately three microns.
 47. Anoptical assembly for a point action camera having a wide field of view,comprising multiple lens elements including an aspheric surface,configured to provide a field of view in excess of 150 degrees thatcomprises an inward field curvature of less than 75 microns, wherein theoptical assembly comprises from object end to image end a first opticalgroup and a second optical group, wherein the first optical group isconfigured to collect light at said wide field of view and said secondoptical group is configured to compensate for distortion and astigmatismerror, and wherein said second optical group comprises multiple lenselements including an ultimate or penultimate lens element that isconfigured with an aspheric departure to compensate for said astigmatismerror, and wherein said optical assembly comprises seven lens elements,wherein said second optical group comprises from object side to imageside, a first singlet, a doublet and a second singlet, wherein saidfirst singlet comprises a biconvex or plano-convex or quasi-plano-convexlens, wherein said second singlet comprises a biconvex, or convexo-planoor convexo-quasi-plano lens, wherein said first optical group comprisestwo or more convexo-concave or meniscus lenses, and wherein said firstoptical group further comprises a biconvex lens.
 48. The opticalassembly of claim 47, further comprising a third optical group disposedbetween the first and second optical groups.
 49. The optical assembly ofclaim 48, wherein the third optical group comprises a biconvex lens. 50.A digital camera, comprising an optical assembly as in claim 47; and animage sensor disposed approximately at a focal plane of the opticalassembly; and a digital camera housing including electronics and a userinterface, and containing said optical assembly and said image sensor inoptically effective relative disposition.
 51. The digital camera ofclaim 50, comprising a third optical group disposed between the firstand second optical groups.
 52. The digital camera of claim 51, whereinthe third optical group comprises a biconvex lens.
 53. An opticalassembly for a point action camera having a wide field of view,comprising multiple lens elements including an aspheric surface,configured to provide a field of view in excess of 150 degrees thatcomprises an inward field curvature of less than 75 microns, wherein theoptical assembly comprises from object end to image end a first opticalgroup and a second optical group, wherein the first optical group isconfigured to collect light at said wide field of view and said secondoptical group is configured to compensate for distortion and astigmatismerror, and wherein said second optical group comprises multiple lenselements including an ultimate or penultimate lens element that isconfigured with an aspheric departure to compensate for said astigmatismerror, and wherein said optical assembly comprises seven lens elements,wherein the optical assembly comprises a single aspheric lens element,which is the only aspheric lens element within the optical assembly. 54.The optical assembly of claim 53, wherein lens elements other than thesingle aspheric lens element comprise spherical or planar lens surfaces,or both, each without significant aspheric departures.
 55. A digitalcamera, comprising an optical assembly as in claim 53; and an imagesensor disposed approximately at a focal plane of the optical assembly;and a digital camera housing including electronics and a user interface,and containing said optical assembly and said image sensor in opticallyeffective relative disposition.
 56. The digital camera of claim 55,wherein lens elements other than the single aspheric lens elementcomprise spherical or planar lens surfaces, or both, each withoutsignificant aspheric departures.
 57. An optical assembly for a pointaction camera having a wide field of view, comprising multiple lenselements including an aspheric surface, configured to provide a field ofview in excess of 150 degrees that comprises an inward field curvatureof less than 75 microns, wherein the optical assembly comprises fromobject end to image end a first optical group and a second opticalgroup, wherein the first optical group is configured to collect light atsaid wide field of view and said second optical group is configured tocompensate for distortion and astigmatism error, and wherein said secondoptical group comprises multiple lens elements including an ultimate orpenultimate lens element that is configured with an aspheric departureto compensate for said astigmatism error, and wherein said opticalassembly comprises seven lens elements, wherein the optical assemblycomprises a single aspheric lens surface, which is the only asphericlens surface within the optical assembly.
 58. The optical assembly ofclaim 57, wherein the optical assembly comprises lens surfaces otherthan the single aspheric lens surface that comprise spherical or planarlens surfaces, or both, each without significant aspheric departures.59. A digital camera, comprising an optical assembly as in claim 57; andan image sensor disposed approximately at a focal plane of the opticalassembly; and a digital camera housing including electronics and a userinterface, and containing said optical assembly and said image sensor inoptically effective relative disposition.
 60. The digital camera ofclaim 59, wherein the optical assembly comprises lens surfaces otherthan the single aspheric lens surface that comprise spherical or planarlens surfaces, or both, each without significant aspheric departures.